I have a large Rubbermaid-type storage container covering my kitty's litter box in my storage room. She used to kick litter all over the place. Now I have much less to sweep up, plus it looks much more pleasant for company.
Turn the container upside-down and cut a doghouse-style opening in either the broad side or the end. Having the opening on the end will make an even more enclosed and private litter box. Use either a box cutter or strong shears, but be careful the plastic can be very tough.
Once you've cut the opening, lay the lid on the floor. Place the box on top of it and snap the inverted container back on the lid. It only takes a few dollars and a few minutes to make a piece of furniture that is completely washable and will last practically forever.