Well, no can do the 4' x 4' design wall. A 48" wide piece of goods won't fit in my Subaru. So I checked what Hobby Lobby had, and found 40" x 60" foamcore board. It's only 1/4" thick, so I bought two sheets to glue together for rigidity. A piece of thin cotton batting so I can pin to the surface and two yards of white flannel (both on sale!) and I will have a portable design board I can store under the guest room bed. A bigger surface would have been better, but I'm going with what I can transport and store. After a little housecleaning in the morning and a drive to recharge the battery of the car parked in the driveway (it ran down again, rats) and I'll get started on gluing it together. The plan is to stick the two pieces of foamcore together with Gorilla Glue (love that stuff), tape the edges for smoothness, attach the thin batting with spray mount, and lap the flannel around the edge and glue to the back with hot glue. I have a scrap piece of muslin to cover the back for neatness.
This will be so lightweight that if I finally make a sewing area in the guest room (I can dream, can't I?) I can hang it with picture hooks.
Has anybody else made a design wall? How did you do it?