Valley fold the two ends together, but DO NOT fold the hidden points. Valley fold and unfold the stubby flaps. Inside reverse fold the stubby flaps. Valley fold as far down as possible. The crease runs through the corners of the hidden flaps.
Valley fold the extra triangles on the bottom half.
Unfold to step 24. Inside reverse fold. Valley fold up as far as possible. The crease runs through the corners of the hidden gussets. The crease IS NOT halfway between the existing creases.