Thank you all!
No, I didn't use a pattern. I just cut the center squares a little larger than I wanted, matched three motifs up, then squared them up before layering. I used two layers of insulbrite facing opposite directions. I cut the insulbrite 1" larger than the motifs and the backing about 1 1/2" larger than the insulbrite. After sewing and cutting the chenille rows, I wrapped the backing around for the border and mitered corners. I slipped a hanging loop into one of the mitered corner folds before top stitching. The main reason for the larger borders, of course, is that the poppy motifs were too small for a potholder.
BTW, I love the Olfa Chenille cutter. It's not really necessary for these small projects, but it's especially great for larger ones.