For two cats, i would do this spuble long and keep it umder a window sill, drill some holes in the back so it can air out, keep both sides totally separate so the cats can have their own space but also keep everything together for cleaning purposes.
27 Useful DIY Solutions For Hiding The Litter Box: Cats are the best, but living with a litter box isn’t exactly an aesthete’s dream. Get inspired with these real projects that range from simple IKEA hacks to complex custom designed furniture.
Minimalist IKEA Cabinet Hack, and lots of other ideas on hiding a litter box. Not just for the litter box but for a dog's or cat's pet bed, when company is over or just during the day, just shut the door and it won't have to be seen until bedtime.
DIY top loading cat litter boxes plastic storage containers with lids feet of grey stair-tread carpet -carpet adhesive double stick tape. I like this idea, but i don't think my older cat would be able to jump out