A very clever puzzle and solution!

If you are holding in your hand a piece of square plywood and a rectangular envelope pouch with an opening, how would you insert the plywood into the envelope pouch so that none of it remains outside of the envelope pouch? 

This was one of the puzzles presented in the 2012 Puzzle Design Competition that went on to eventually win the 2012 Puzzle of the Year Award.

If you have not solved this puzzle by yourself, then watch the video!