Step 1: The Beginning
2. Find some tape, duct tape will work the best.
3. Destructure the box and lay it flat.
Step 3: Fold the corners
Step 4: Fold up the open side
Step 5: Halfway there..
Fold the leftover box flaps over so that a triangle is formed. Tape those flaps down.
Open out from the middle and flatten the opposite way, this may take some serious beating up of the boat, but make it work so that it is in a diamond shape.