My LQS uses a large piece of batting tacked to a wall for their design wall. This works very well.
I went out and bought a large piece of felt and hung it on one wall with curtain rods. I use the rings that have the hooks on the bottom for easy removal of the felt. I did scruff up the felt a tiny bit with a brush to make the blocks stick better. It works very well and with the curtain rod, makes it easy to put up and take down, plus I can interchange with another piece of felt for another quilt, without removing the first quilt. I like this benefit.
I have also heard of using an old fleece blanket or flannel.
IMHO, I would bring a square with me and go to the fabric shop and just plop the square onto the fabric. Give a gentle shake. It the block stays, the material will work just find.
Hang it wherever you have a large open space. I have mine hanging over a double closet door with the bottom pinned up for larger quilts. It works much better with a firm wall or cardboard behind the design wall.
Hope this helps! :) :) :)