Otdfbt

One approach is to look at shoes used by people with upper-limb amputations or who were born with missing upper limbs.

While your characters are not human and may or may not have partial or full use of hands, the basic premise is the same: how to keep your feet clean so you can use them for hand-like tasks.

Diamond Excell was born with no arms and uses her feet for everything she can. Slip on shoes without socks are what she, and other foot-users seem to prefer. There's a picture of her in some boots at 6:30 in to the video, also 7:02. Her goal is to start her own shoe line.

When she cooks, she sits in a rolling chair in the kitchen so she has use of both feet at the same time.

Jessica Cox, who also has no arms, uses slip-on shoes and sits in a chair if she needs to use both feet together.

A wide variety of shoes are easy to put on and off without use of your hands.

Moccasin slipper shoes with light soles (for indoors and occasional outdoor use) keep feet clean and dry and are easy to kick on and off. You can throw these in the wash too, though not too often.

A low boot would work for outdoors.

Or just plain old slip-on shoes.

Now, your characters do not have human feet, so obviously human shoes aren't going to be an off-the-rack possibility.

I will encourage you though to consider enclosed shoes like the examples I give. Note how people who rely on their feet to do things hands usually do aren't in flip flops or sandals most of the time. Why? Because feet get really dirty in open shoes. Sure, the sole of your foot is protected from stuff you might step in, but I think you underestimate the effects of dust, dirt, mud, and random uck. Far more than you'd pick up with your hands.

Indoors your characters would keep floors very clean and use rugs or carpets to keep dust and grit off of feet. Then they'd go barefoot. They would slip on shoes whenever they went outside.

The other consideration is cultural. We think dirt is unhygienic and gross. But no animal wears shoes and many use their paws/claws/etc to pick up or manipulate food, or they lick their feet directly.

Any glove-like shoe will also work. There is a significant number of shoes in human history that didn't have a separate rigid sole, but were wholly made of soft leather - native American mocassins, early medieval Germanic shoes, chuvaki of people of Near Asia and Caucasus. Such footwear works quite good, unless you need to walk on paved surfaces regularly. From my personal experience I can tell that they are very comfortable in the forest.

For humans, such shoes are usually made as soft leather 'bags' for feet, but nothing prevents them from being made more glove-like for someone with longer and more mobile fingers.

As for more technological solutions, right now there exist a number of 'barefoot' shoes of sturdy synthetic fabrics with very thin vulcanized sole. Some of them, like Vibram Five Fingers even have separate fingers.

So, leather foot gloves for low-tech settings and synthetic gloves with rubber gripping surface for more advanced settings. As for the flip-flops, they can be worn over such foot-gloves when you need to protect them from abrasion - in something like medieval urban settings. In our world, medieval townsmen had worn wooden sandal-like pattens over soft leather shoes to protect them from wet, dirt and abrasion on cobblestone.

UPD: that may be a part of much bigger issue of how a race that uses the same extremities to walk and manipulate objects will structure their houses, cities and living in general. It will not be much of an issue while they are living as hunter-gatherers. As soon as they get agriculture and animal husbandry, they get problems - you do not want to eat with something you just mucked animal fecal matter with - the rate of stomach infections will be just too high. The same goes for medieval-style cities with horse-drawn carriages in the streets.

I can see feet cleaniness being a big issue, foot-bath being more important market of 'house entrance' then a door. Helping the guests to wash their feet would be even bigger marker if respect then it was in human archaic cultures.

Possibly, the structure of the cities would be different, with streets for walking being even more separate from the streets for carriages and pack animals. It would rather look like a system of sturdy poles and narrow bridges raised over the ground level.

Street food and it's consumption will also look different - from forks or other similar eating utensils being always carried on one's person, up to vendors putting the food directly into the customers' beaks.

The results for the footwear are as follows - glove-like closed shoes are better for situations where you can encounter a lot of dirt and muck. The are also better for raised walkways and poles, since the don't interfere with feet grabbing the surface you walk upon. Sandal-like footwear is more comfortable for situations where you are not that likely to encounter much dirt - for example, indoors, in big buildings where there is not much dirt, but it's impractical to wash the floor all the time.

Elevated clogs (geta) with toes hanging off the front.

https://en.wikipedia.org/wiki/Geta_(footwear)

In a therapod or bird like foot, the toe to sole ratio is much longer than in a human. We have short toes and lots of sole. Birds have long toes and small soles. Therapods would definitely use their toes to run, as an ostrich does.

But this is polite society. Just as running in geta would be trickier than barefoot, these dinoshoes make it more difficult to run. They support the weight using the sole and keep the toes clean and off the ground. If something must be grasped, the long toes protruding out past the geta are clean and ready for the job. The shoes stay on.

Does the grasping surface of the foot need to be the same as the walking surface? What if they were on opposite sides of the foot? A foot physiology where the toes bend "upwards" has certain evolutionary advantages, since it would allow your characters to walk while holding items at the same time.

To put it in more familiar terms, it would be somewhat like a human hand-walking on the back of their hands. For us, doing so would probably be rather hard without significant damage, since our wrists are not quite meant to bend like that, but it does not have to be the same for your folks.

As for footwear, I imagine that open-type shoes, like flip-flops, would perform quite nicely when no protection from the elements is required. When added protection is needed, a glove-like sock made out of cloth or leather would probably be sufficient.

I'm not 100% certain that you're asking the right question. If you watch a raven solving a puzzle, they tend to use their mouths for "hand-like" tasks, rather than their feet.

Regardless, I should probably answer your original question... :-)

I suggest a dynamic mechanism that opens and closes the shoe based on body position/foot height.

The context in which "hand cleanliness" is important are by definition almost always contexts that are not on the floor. Other than picking up something that has accidentally fallen, one would tend to want shod foothands on the ground, and unshod foothands when the foot is being held at a higher elevation.

So I would suggest a mechanism that is anchored to the hip or body (depending on articulation), and that "opens the shoe" when the foot is elevated above the ground. Lifting up the foot, in order to use it as a hand, would expose the clean foot instead of the dirty shoe.

Alternatively, one could have the same type of mechanism enclose the foot (and, of necessity, the shoe) in a "clean glove" when the foot was elevated, and remove the glove when the foot was put back into walking position. This is inferior (for reasons of dexterity) to the "open the shoe" approach if the avians wear shoes. But bird feet are not like our feet, and I think it's likely that avians would end up going barefoot most of the time. If so, then an automatically-applied glove would provide almost as much dexterity (no double-layer problem with shoe + glove), and let the birds continue to use their preferred barefoot walking style.

As to the specific engineering of the openable shoes or closable gloves, I think that involves more specifics about foot articulation than I have access to.

Just a fun idea, but have you thought about wheelies?

I'm not sure about what sort of era that you are going for, but you could have a wheel+stopper combination. Something that looks like a fingerless glove, but for the feet and it goes up and get's slightly bulky on one side of the ankle. Have the wheel be able to pop out from the ankle and slide under the foot in a hooking motion, maybe something locks into place on the foot-glove, so that way your weight can directly supported by the wheel.

Have a stopper be placed near the back so that way you can just rock your self backwards slightly and stand in place on it or slow your movements down. It could also be semi-attached to the wheel mechanism and comes down when the wheel does. Maybe a special button you can press on the ankle to unlock the wheel to move it out of the way & back to it's ankle cartridge/spot, if what you are doing requires use of the full palm of the foot.

It'd give you movability and keep your feet of the ground. This would only be viable in a modern environment, with paved roads/sidewalks and non-carpeted buildings. The palm of the foot glove could be well padded or designed to evenly distribute the weight/pressure across the whole palm of the foot. Walking up stairs or inclines would be okay, just center your body of the stopper instead of the wheel.

Maybe the answer is in your very question. Their feet are always dirty. And, since they are bird-like, they might consider sheathing their talons to be a bad thing.

So when they need to do something where they need their feet clean, maybe they wipe off their feet using a cloth they keep for just such occasions and grab tools appropriate to the task. Like for eating they pick up a spoon or knife-like utensil. Similarly, they have gloves that they wear when they need to handle something they want to be kept clean from whatever they walked in or perched on.

I imagine their talons would mean their gripping mechanism is different from their sensing mechanism. They could tell something about an object by scraping it and tapping with their talons (or beaks) but soft delicate objects might not work out so well. So where we feel with our fingertips and then our other parts of the hand, they start with talons and then use some spot on their foot that if it got burned or cut, they would still function until it healed.