I have tried every kind of pet bed, towel, blanket I could get my hands on, and most were just not big/washable/slip proof enough. So 2 weeks ago I saw a giant bathmat that supposedly has "gel" inside at Costco, and decided to give it a shot. It covers almost half the cage and my bunnies LOOOOOVE it. They snuggle on it all day. It doesn't move around or fold over or crumple up. It catches A LOT of hair, so much so that I vacuum about 1/4 of an inch of hair off it every day (better than it floating around my house!). But the greatest thing of all is that my mini rex with sore hocks has had a huge improvement in the look of her heels. They look amazing, no red marks, just regular pale skin.
I bought a dark brown one so stains won't show. I'm going to get 2 more to rotate out, should they discontinue them. I highly recommend these.
Disclaimer: My bunnies are not chewers..