Meade, I usually like the peace of mind that stitching gives me and usually use a fairly heavy duty needle and thread and a pair of needle-nosed pliers to push it through the heavy material (carefully!). However, on the patch you recently sent with me, I chose a placement on my bag that had an inside tool pocket that precluded the use of needle and thread. After trying a hot iron without success, I heated the patch slightly, then used a hot glue gun on the backside. I was careful not to get too close to the edge (back of) the patch, but not so far that the edge would lift eventually. Then I burnished it while still hot. A small amount of glue creeped outside the patch's edge, but was very easy to scrape off once dry. An important tip would be to not overdo the amount of glue applied, while covering as much of the back of the patch as possible.
Only time (and maybe temperature) will tell if this method works, but it lays flat now. If I could, I would put a small stitch into each corner for insurance.
Paul Germain
Midlothian, Va.