I've only ever kept my bunnies in the house. When young, use a cat litter tray lined with newspaper and covered with paper shred, straw, or whatever you prefer. Put a bit of hay at one end or some treat so they will happily sit there munching away while they do their business. As mine got older I changed to a deeper box like those coloured stackers for toys as they do tend to spray a bit. When they jump out there will always be a bit of paper or the odd carling coming with them but hey... When you change the box, pick up a few of the old carlings and put them in to remind them that this is the toilet. The downside is that they do love a bit of wire to chew and if you catch them at anything else, spray it with a deterrent you can get in pet shops. Of course they must be put outside to have a run around and eat some plantlife. If your garden is not completely secure, a run with water and shade/shelter is good. Lots of fun having them inside, good luck