The easiest solution is to get an inexpensive kitty litter box. Half fill with playground sand and add about 2 cups of food-grade DE. Put out in the yard when the weather is nice. Put in the coop (if there's room) when it rains. I have 12 hens in one pen that share 1 box and it's plenty. You can see it on my livestreaming cams at www.HenCam.com (it's the purple plastic box.) The hens use this daily and there's not a louse on any of them.