From what I've seen on tv, I think the first step is sketching your "window" on freezer paper. One show I saw did it sort of like reverse applique', with the pattern cut out of solid black cloth then the colored fabric was attached under it in the opening. But I don't remember how they did it. You might see if you can find the Simply quilts videos on HGTV.com and see if they have one on file for it. The finished product was really pretty.