Sometimes it helps to provide natural chewing options for them. Things like natural untreated wicker baskets, apple and willow branches, a 1x2 pine chew block(thoroughly dried), hard dried pine cones. But with some rabbits bunny proofing is the only thing that works. Try and make it so that your bun can't get to the edges, or you can sometimes use chew proof edging that is metal or hard plastic, to prevent the chewing. Also providing activities like a dig box or an old phone book to shred, make good boredom breakers. If all else fails, use a chew proof flooring like ceramic tiles, or sometimes heavy duty horse stall mats work well, though they are very heavy.