It depends on how you like your snaps. If you like them hidden, you'll attach the snaps first, then sew up the dipe. If you like them exposed, you can do them last. You probably know this, but just in case...if you're doing hidden snaps, you'll want to attach them to your outer and hidden layer, or if you're not doing a hidden layer, you'll want to add some interfacing or small scraps of fabric to give extra support to that area.