I bought my flannel cover years ago but finally just put it up last month. Yes, I know it took awhile before I finally had a moment when nothing was on my design wall. Anyway, I'd also had bought the 2 insulation boards at 1.5" x 4 x 8 and cut them down to fit my space. I used screws with large heads to attach it to my chipboard down here in the basement, then used 505 spray over the insulation board to attach the flannel which was 120 x 120. I'd trimmed it down leaving at least an extra 2 inches to wrap around the edges of the insulation board. Of course my ornery kitty found a loose edge and started playing with it so I went around the sides with straight pins so she couldn't remove it on me. So far it's worked very well for me. I'm so glad I bought what I needed years ago as I didn't realize the prices would jump so much due to the pandemic and greed.