I had my foam board cut to size before bringing it home. Finally goy it put up after waiting close to 5 years to do so. I found online a flannel in a 3yd x 3yd size so 108x108. I'm in the basement with low ceiling rafters plus a baseboard heater at the bottom so could only make it 70"H x 96"W, the size of 2 - 48"x96" foam boards. The cutoffs were given to my sister. I used 505 spray to adhere the flannel over the boards. I cut it 2" more all around to go around the edges and tuck it behind. My foam board was 1.5" thick. Sorry no photo of it as my PC is in the shop right now.
When I brought it home, I had them strap it on top but loosely so not to damage it. It sat in my garage for nearly 5 years and never got damaged which to me was a miracle.