You will need to buy some insulation board and screws, oversized flat washers, felt and plastic edge trim available at Lowe's.
First, decide what size you need, then mark and cut the insulation board to size. You just need to score the board, then you can snap it and it will break neatly.
Mount the insulation board on the wall using a screw with an oversized washer behind it. You will want to find the stud, to make sure the screw is secure.
Notice that mine are near the corners but are secured to the studs, so they are not even, this is not a problem, as they will not show once you are finished!
Now cover the insulation board with felt by tucking it under the edges.
If you want to secure it with pins along the edges you can, but it is not necessary.
Then cut the plastic molding to size.
Or have your husband do it.
And slide it into place around the edges.
Leave enough room at the corner, for the other side piece to fit flush.
It's a very small amount of "settling" but you will want it to be nice and tight once you start using it.
The felt can easily be replaced if you ever need to.
Please let me know if you have any questions! I do hope you find this helpful if you are going to be installing a design wall any time soon.
Enjoy every stitch!