During the winter I mix wood ash, pine shavings, and sand together and put it inside of an old tire and the girls know what to do. Mites are a much bigger problem in the winter and the chickens need to have a place to dust bath.
Sounds as if trying to take a dust bath and has only shavings. Needs soil, wood ash, diatomaceous earth, and such to make a proper bath. Mine like to dig in the dry soil beneath the coop and bathe.