I started with a 4-1/4" x 11" piece of white card stock. I punched one edge, which left me with 4-1/4" x 10-3/4". Starting from the punched edge, I scored at 1" and 6-1/8". So when my card is all folded up, it measures 5-1/8" x 4-1/4".
I used some red line tape to adhere my flap at the crease. That way it leaves enough room to tuck in the card front, and also be tight enough to keep the card closed.
I chose some Lizzie Anne Designs paper (Winter Wonderland) to go with my penguin (from the Way Up North set), and accented with a few glittered snowflakes.
I hope you get a chance to play along. If so, use keyword ssnotime113 when uploading to online galleries. And here are links to the talented Stamp Simply team samples: