A dog crate tray is around 1" deep which is no good for containing litter or hay and can leave a lot of mess outside the crate. To solve this issue you can create a frame around the base of the crate using wooden skirting, Perspex or corrugated plastic (e.g. Correx). A deep tray (e.g. a storage box) containing any litter and bedding is another way to reduce the mess.