Right now, the girls go into the coop to dust with the wood shavings inside. I have access to alot of spent wood ash, and sandy garden dirt, but to place a box in the open run with the ash and or dirt in it, my concern is after a rain would they still be able to use it? And since their used to using the coop, will they take to the box if I make one? If I put one under their coop how deep and wide should it be made? I really didnt want to dig a hole in the yard, and with all 6 in the coop it gets kinda crowded for em...since they all seem to dust all together and at the same time every day. And those of you that have followed my "soft shell" thread..the problem has been solved!