Shortly after I finished my quilt top, I was asked to make the "connect the dots" block from the Block Party book for an online quilting bee. The bee member asked everyone to try "windowing" the applique and sent us all a helpful video from the Fons and Porter site to learn how. It worked like a charm, but was unfortunately too late for my very stiff "e"! I thought I'd share the tip in case there were any MMQG members who hadn't heard of it.
You will need:
Double sided fusible interfacing
A template for the shape you are appliqueing
1) Trace your design/shape onto a piece of double-sided fusible interfacing. Draw on the smooth paper side, not the bumpy side. If your shape is directional, make sure you trace it in reverse as you will be fusing this onto the back/wrong side of your fabric.
2) Cut out the interfacing, leaving about 1/4" extra on the outside edge. Don't cut directly on the line that you just traced, you'll cut along the line later once you've fused your interfacing to the fabric.
3) Cut into the middle of your interfacing shape and around the inside about 1/4" from your traced line. Your interfacing will now look like a cookie cutter. This is really the only step that differentiates "windowing" from regular applique.
5) Now that your shape is fused to the fabric, you can cut along the line you traced on the paper side of the interfacing. Peel off the paper backing from the interfacing.
6) Place your applique'd shape on top of your quilt block/background fabric. Press in place and stitch around the edges as you normally would to secure it permanently to the fabric.