I got my felt at a local specialty fabric shop called Seattle Fabrics, but I know that Joann has wide bolts of felt too. You can also use batting king sized.

I've actually done a side by side experiment of my synthetic felt and a cotton, heavy duty flannel. They have equal holding powers. Neither does well with blocks with a lot of seams and bulk but both hold basic blocks just fine.

Thank you RST that is exactly what I wanted to know. Without doing a side by side test. Nice of you to reply with your results.

I found that fleece (also available in wide widths) does ok, but not as well as flannel an felt. I still consider it a viable alternative though.

I just put up an old piece of flannel tacked to the wall in my sewing room. I am piecing a queen size Charming Addition and a design wall is a must with that one. So far the flannel has worked just fine.

I use an old flannel sheet.

Never even considered washing my design "wall". I do go after it with a clothes brush now and again because of the little threads and fabric detritus that ends up sticking on the board. Works wonderfully and leaves my wall just like new! I would go for the best deal felt or flannel and the color you like best, white or cream.

Heaven! I wish I had read something like this before I made my design wall. I used green insulation board, covered in felt, and then added a layer of batting. Six months latter I find myself standing and picking threads off the batting like we are a pair of monkeys grooming.
Gotta go now, I have to go take off a useless, and thread filled, layer of batting!

I have always used flannel. When you wash it, blocks will just stick to it. I don't think that felt would have the same type of magnetic qualities that flannel has. Buy your flannel when JAF has the flannel on sale. Pick a good quality of flannel.

design board
 

I got some fleece on sale and used that. It woks very well and if it needs to be laundered not a problem. I used a pale yellow.

I've used a king size piece of warm and natural batting. When it gets stringy, I just use a roller picker upper and it works great. I've had the same piece for 8 years now with no problem.