My chicken run is around 7'x12' and I'm needing to redo the dust bath. Last summer I used my daughters old turtle sandbox but it just took up too much room and because I hasn't drilled holes it was a nasty mess if I didn't get the cover on fast enough during rain. My run floor is rock so I'm thinking of building just an rectangle frame (no bottom) and simply sitting it on the rock and filling it with sand. If I don't have a cover for it will having no bottom allow it to drain enough? I realize I might have to rake it a bit to mix it up, and replace sand that might get swept away with the rain. I'm thinking about putting a cat litter box with lid in the coop as well but I'm worried that they will end up fighting since that would be so small. Helpful opinions???