First print out two copies of the basic pattern. Cut out the strap and front and back pieces on the inside, darker sewing line. NOTE: Add 1/4 inch to the sides of the back pattern for the closure. You can have the shoulder straps go from back to front or front to back depending on your design. Then trace the pattern on to felt or Ultrasuede or any other non-woven fabric. That's it. Now you can add trims or pockets or anything else like decorative edges. Use snaps or Velcro for the back closure. The straps can be closed by snaps with decorative buttons (I used two of my toggles) on the top for decoration.
