She sounds such a character! The laying bin should be about 12 inches deep. I used a mix of play sand and compost. It needs to be damp enough to hold it's shape, so that when they tunnel it won't collapse on them. Lily always digs into a corner rather than create a tunnel. I always have two laying bins in for Lily so she can choose the right place. My girl is so sweet and friendly, plus I love the more rounded body shape of the females!