I just put my sand right on top of the dirt. Nothing in between. Clean up any wood chips or shavings so the sand will stay drier. And use at least 4 inches of sand as they are going to scratch around and dig thru it. As deep as you can afford....4 to 6 inches is best. I only have about 4 inches in my coop and run. Occasionally they do dig down to the dirt, but I just rebury it.