Elastic Sewing Cheat Sheet
Open out the shoe and place one side of the elastic just behind the ribbon in the same diagonal angle. As shown by the red dots.
Stitch one edge of the elastic down and then stitch the other, you do not need to stitch this in a rectangle like the ribbons.Just along the sides as illustrated in black.
Once one end of the elastic is stitched, position the other end on the other side of the shoe, opposite following the angle of the ribbon as you did on the first side. Be sure to just stitch down the edges and not in a rectangle.
Voila! The elastic should now be stitched in a loop across the instep!