They love to sit on top of pieces of wood

They love to sit on top of pieces of wood and also you can make a great hiding place out of large bits of tree branches. If the branches are sturdy enough you could place a flat piece of ply wood on top of the branches so your rabbit can jump on top and crawl underneath amongst the branches. Contact a local tree surgeon or gardener to let them know you would be interested in any off cuts they may have. Make sure they come from trees that are safe to rabbits.