Start by determining a layout and piecing a patchwork square that is the same size as your napkin (mine were 8" x 8"). Next, assemble the patchwork square by stitching the pieces together. For mine, first I sewed the pieces on the center strip together, then I sewed each outer strip to the center strip.

This left me with a slightly wonky square, so I squared off the corners with a quilting ruler.

Next layer the pieces as follows: 3 layers of batting (this was me being paranoid, which worked out well. In the future I’ll use insulation batting.), patchwork square (right side up), cocktail napkin (wrong side up). For mine, I placed a little tab of fabric (for hanging) in between the 2 fabric layers. Start sewing about 2 inches from one corner of your fabric stack, continue around the next 3 edges, then sew about 2 inches back into the first edge (leaving an opening). Trim the batting and turn the whole thing inside out.

Next, handsew the opening shut, then machine stitch an "X" shape from corner to corner on the mitt. Voila!

Here are my two hot mitts, hanging out.