I do not glue. I use Best Press on the handkerchief, and then fold it twice and iron the folds. I also fold the background square and iron it. Then I center the handkerchief on the square matching the fold lines and use regular straight pins to hold it in place. I machine applique with a zigzag stitch with invisible thread. I also hand applique with invisible thread, which isn't easy because you can't tie a knot in it. I take a few stitches in the square toward the edge of the handkerchief, a few stitches away from the edge, then a few back to the edge and start my applique stitches. It holds the thread without a knot.