My design wall is very portable, removable and can be folded down to a 12" square. All I have are 2 flannel backed tablecloths that I got at the thrift store for 99 cents each. My DH installed 3 hooks at ceiling height on the wall for me to hold 3 clip hangers. I clip the table clothes together with the hangers and hang them on the hooks. I can use one for a smaller project or both for something large. If I want to take them down, I simply unclip them and fold the tablecloths up. The hooks are not noticeable. I have been using the same 2 tablecloths for 3 years and so far they are still working great. Total cost of my design wall? $3.00. I already had the clip hangers. They are the kind you use for skirts or pants.
Oh, and if the project becomes too heavy to stick to the flannel, I can clip it to the hangers themselves rather than the flannel.