Here in Vermont, the ground is frozen solid all winter. Chickens are inhibited from their natural way of staying clean and preventing infestation of parasites.
All it takes is a pan or box and some clean sand. The chickens go wild for the experience and defend their turn until they have completed their toilette. It is really fun to watch and clearly a pleasure for them.
I use a rubber feed bucket. I tried a metal feed pan but the sides were so low that most of the sand gets kicked into the bedding. It does no harm if some gets spilled but requires more frequent refilling. The feed bucket is about 8” deep and 24” across and helps contain the sand. It accommodates a chicken very nicely and often another will climb in for a shared bath.
Use clean sand, such as Quickrete tube sand which is inexpensive and free of harmful additives. You can also use play sand which is made for childrens' sand boxes.
You will find many suggestions of potential additives for a dust bath. One of them is diatomaceous earth. I strongly recommend that you don't use this. It is made of ground fossils. Under a microscope, you will see that it is made up of tiny shards. It is hazardous to your chickens. Breathing it can cause tiny cuts and it sticks to lung tissue causing scarring in the respiratory tract and lungs. It can cause great pain and irritation to the eyes. Giving your chickens a big pan of diatomaceous earth for dust bathing is to invite them to breathe clouds of abrasive, damaging dust.
Adding fragrant dried herbs (catnip, lavender, sage, oregano, rosemary, basil, pennyroyal, wormwood, yarrow) to your nesting boxes and replenishing them when the fragrance fades is a much more effective way of preventing pests in the coop, either in the bedding or nesting boxes. Essential oils of these herbs used sparingly, such as a dab on the wall, are another option.