I will list is as i installed it.

Start by checking all your seat springs and repair as required first.

Get some heavy cut pile carpet and cut it about 4" larger on all sides. This overlap will be the section that you roll over and down the sides. Install Carpet backing side down on springs. NO under carpet cushion is required. The rolled carpet provided a nice soft edge where the thick perimeter seat wire is. It will not allow the wire to show thru the seat cover.

Hog ring the carpet down all the way around and cut the corners as required to allow for a nice folding around the corners. next i used some high density memory foam from the local fabric store. The LMC one was way too soft and was garbage quality. I cut the foam just 1 inch larger than the seat profile all the way around. Next i just installed the cover and clipped it on.

The back was done the same way but i never added any foam at all. The seat cover already has a padding installed and with the carpet behind it feels nice. The foam in the back pushed me so far forward i was sitting too straight up.