Putting slightly less, just slightly less, will help. Rabbits will paw through larger piles to get the best strands, and when they do that, they push the hay to the other side, so then the entire body rotation happens to research the previously pushed aside pile, which is now at the other end of the box.
A litter screen will help as well, because it’s easy to dump everything off it. It lessens litter flying around and makes cleaning more clean? No loose hay caught in litter and such. If you look at Wick’s Instagram, you can see how his litter box functions and it generally saves him from peeing on his hay.
http://www.instagram.com/p/BaPzvpkFcN-/
http://www.instagram.com/p/BXsXo28FTcG/
Wick’s litter screen is just made from cut knit mesh, which is something you can buy in large packs cheap online. His is 7-count (denotes how big the squares on the mesh are. 7 is small to catch poos and be solid, but large to let urine seep through).
The answers provided in this discussion are for general guideline purposes only. The information is not intended to diagnose or treat your pet. Seek the advice of your veterinarian or a qualified behaviorist.