Then I used the 1-1/2" paper punch to cut out the shapes.
I cut the "thread" holes with a regular hole punch (1/4"). When I punched them out, they all looked lop-sided and uneven, but it didn't seem to matter when the buttons were finished.
I put them in a 325-degree oven and watched them for a couple of minutes (the whole process took about 3 minutes). The instructions that came with my plastic instructed me to place the plastic on a piece of a brown paper grocery bag instead of aluminum foil as in Susan Beal's article, so that's what I did. They curled up a little while in the oven, and although I followed my instructions by pressing on them with a pad of paper for about 15 seconds while they cooled to flatten them, I don't think I really needed to do that. They seemed to flatten well on their own. Here's what they looked like when I first took them from the oven.