I use the closet door in my sewing room, just covered it with felt and away I go!
Also made one using one of the science fair display board (which you can pick up in Wal-Mart) and covered it with felt. This one I use at Guild meeting retreat or any where else I need a portable.
If you make your own be sure to use a light neutral colour fabric (mine is cream) that way it should not conflict with your fabric colour when you are working out a design.