Gel Holder Snaps
To mount the magnetic snaps I used the gel to find the right positioning. I put the nipple side of the snaps (#1 and #2) on the thick 6mm foam and the dimple snaps (#3) on the thin ~2mm foam. The key here is to make sure the gel will at least cover the screen when mounted.
To actually mount I pushed the snap in place only hard enough to leave a mark, then pierced a slit with my finger nail trimmer scissors. Then slipped the snap through the foam. It has a plate which the prongs go through and then bent the prongs around the plate on the opposite side (Shown in #4 but the mounts look essentially the same on the other side through the 6mm foam but a little less metal wraps around).
I put some electrical tape over the magnet on the dimple snaps mounted to the thin foam (Shown in #3). Without the tape, these snaps have a hell of a grip and the gels will not swivel and you'll have a difficult time removing the cover.
The two pieces of foam don't end up flush together (see side view in #5) once the cover is mounted. This is fine, the snaps do all the holding work for the gel, so the cover is just to look pretty and keep the gel from blowing around too much.