I made 2 of these design walls from insulation board. One larger than the other. Neither is hanging on a wall though.
I used felt on both. I was given large amounts of felt yardage, so I used it. One was a baby blue. The other ...dark green.
One I used upholstery nails to hold the felt on. On the other, I used purple duct tape. The nails keep falling out (so did staples before the upholstery nails), but the duct tape is still holding up well after about 4+ years.
They work great for holding up blocks, but I tend to use pins anyway, just in case.
I also find that I don't like the colors. I often hang a length of batting over the board because I like working with the neutral color better than blue or green.
They are both portable. The reason they aren't hanging on the wall is, I also use them to extend the width and length of my sewing table when I want to fmq with my little (domestic) machine instead of the longarm. I taped heavy plastic to the back, and I made a little cutout near one corner that slides around my machine perfectly. Like this:
https://www.youtube.com/watch?v=yAS25v3ZTk0
I also have covered a small (18" x 24" ) piece of foam board with batting to use for just a block or two.
Sometimes, it's easier and faster to just tape a cheap $store table cloth to the wall when I'm using the big board as a table top.