Got a wood stove? or access to someone that is burning clean wood?
Make sure this is clean wood ash, no burning garbage or plastics or anything else in the fires. (and yes I do know people that will toss and burn things in their stoves)
While the ducks love to snow bath all winter long, the chickens do not really like snow and while its not a issue in terms of their health, winter time in the coop tends to be the worst time of the year for lice or mites and a free access ash dust bath can go a long way to reducing this possible issue.
Just get a box shape, whatever suits you, I used cardboard and fill it half full, don’t worry about sorting out any bits of charcoal, the birds will break it down and anything left when you go to dump the of it in the garden or compost pile, its just active bio char at that point..
In keeping with that, any ash they get out into the bedding is just going to sweeten and help your coming spring compost pile when you clean that coop floor.
Let the chickens do the rest of the wood, they will dust at will, shaking off any excess and as clean wood ash is edible for them as well, they will not hurt themselves in any way as they finish their pruning with beak etc.
I do this in the chicken house and in the summer have one out of the coop as well. They truly love it and I don’t seem to have as much “dirty butt” when they use this. My saved pumpkin seeds help with the “dirty butt” so I assume they have some type of worms. I use apple cider vinegar in their water when they have this too. I guess both doesn’t hurt.
Mine do love their pumpkin/squash seeds, I try and grow enough for storage that they get at least one cut open per week or more when possable. I have never thought to do it in summer, I use the ash in the compost and gardens in summer time and they use their favorite sand or dirt bath area’s interesting, I might have to try adding a bit of ash to their favorite summer spots as well