This link will take you to the video.
Here's my version:
Opened up, it looks like this:
The measurements provided are as follows: Take a 4 1/4" x 11" piece of medium weight card stock and score at 2 1/2" and 6 3/4" along the 11" side. If I give this card with a gift card, I can create a pocket on the lower panel to place the gift card!
SU Butterfly Basics and Sweetly Framed.
Stamp Up a Storm includes a nice how-to video:
Here are a few more flap cards on Pinterest: