I've had Lawn Fawn's Ahoy, Matey stamp and die set for a while but hadn't used it yet. My design idea is not original, I've seen many variations of this all over Pinterest.
I used black ink on Kraft cardstock, aged a bit with Distress Inks in a few shades of brown. The flaps were made with a Lawn Fawn's Lift The Flap die set. The dotted lines were done with a Copic multiliner.
The die cut images under the flaps and on the inside were colored with Copic markers.
I don't have a better view of the cash slot but I will explain what I did to create it. The image that you see above is one piece of cardstock with the largest flap from the die set used. I used another piece of paper under this flap to make the cash pocket. I used an oval die (Oval Word Frame from Die-Namics) to cut the opening. I glued this under the Happy Birthday flap piece, then used a tape runner to glue this assembly inside the card. I was careful to make the line of adhesive narrow on the bottom edge to allow the cash to be tucked inside, a line of tape along both short sides, and a double row of tape over the top opening so that it wouldn't pull off the card base when the cash was removed.
The card was well received by the 8-year-old recipient who felt the envelope before opening the card and announced that it felt like money. He knows me well!