Press, press, press! Also use at least a 16ga needle and go slow. Your trouble spots will be the corners, where the bulk will be. Yu can eliminate this by mitering the corners.
Fold each corner in like a triangle, so that each cut side of the triangle is 1 1/2" (the third side with the fold will be longer, and that's okay). Press. Now fold in each side 1/2" and press, then fold again 1" and press. Slowly stitch about 7/8" away from the outer edge of the fabric. Your corners will not not be bulky at all, and your needle won't break trying to sew over 9 thicknesses in the corners.