So, my cling foam arrived and I was able to mount my sentiment stamps. Following the directions of a video I found on youtube a few weeks back, I got to work.
Step 1, trim the outside edges a bit.
Step 2, cut the cling foam to size and peel off the paper on the sticky side. This stuff is VERY sticky, and will muck up your scissors when you cut it (ie, you'll get sticky residue on your scissors). Use an eraser to get the residue off when you're done.
Step 3, with the rubber on the foam, cut the different sentiments apart. This is fairly hard to cut, as the foam is quite thick and the rubber tough.
This is a bonus step. After peeling the front paper off (the side that clings to acrylic blocks), I used a Copic (ie permanent) marker to write the sentiments on the front. I figured it would be easier to find the sentiment I'm looking for if I can read them faster (and while I can read backward script, why put myself to the trouble?).