They worked out great. Perfect size. I got them at Target for something like a $1.50 a piece. I used all purpose sand (home depot) in the bottom to weight them down then topped it off with the wood shavings. I haven't had to clean them even when I had them in the dog cage.
Tried the grass clippings in the storage shed/coop, not a good idea. Loaded with ticks, I'm pulling them off me every time I go in there.
The sand works well and keeps everything dry. I did lots of reading here to see what people have tried.