Originally Posted by ontheriver
Several people have said they use flannel like the back of a picnic table cloth. Do a search on here, you will find many ideas.
Fleece works great too. I've put up fully assembled quilts on it and it sticks without pins. A bonus of the fleece is the width. I used black.
There's also a flannelette product that has grid markings on white that is great for placement and keeping all straight.