1: Begin by folding the top down to determine the center line, then open flat
2: Fold opposite corners into the center at 45 degrees
3: Fold the outer raw edges in to align with the inner raw edges.
4: Now fold the blunted corners at 45 degrees to lie along the center line where you will tuck the flap into the small triangle shaped pocket see #5.
Turn over to see the front of your envelope.
What is fun about this is you write your letter on any regular sized paper, decorative stationary works well. Fold, add a decorative sticker to the back and address the front. Yes people you can mail these with no problem. Save on envelopes.