In my experience, some cats don't like dark caverns so I added some holes in the top for light. I used my 1 1/2" holesaw again to make 8 holes along the outside edges. Pic 2 shows the interior of the box with the lid in place.
All you need now is some litter and a quick prayer your cat will actually use it. Cats can be picky but what's not to love about this box. Our cat, who is very particular, has been very happy and we've been pleased to not have the dogs in the litter box anymore. Hope this cheap & easy project makes your critters happy as well!