: Make a crease by folding the bottom left edge to the crease along the dotted line.The folding of the bottom right edge is the same as that of bottom left edge.
: Fold on the crease.
: Pull out along the creases made in step 11.
: Turn over.
: Make creases along the dotted line.
: Fold according to the valley fold lines.
The black dotted line is valley fold line.
The red dotted line is mountain fold line.