Watch the video: http://pbskids.org/designsquad/build/floating-box-pop-card/
Step 1: Here’s What You Need to Make Your Own “Floating Box” Pop-up Card!
General art supplies for decorating and writing messages
Step 2: Cut Two Slits
On the crease side of the paper, make two straight, inch-long cuts.
Step 3: Define the Tab
Step 4: Make the Box
Once the box is in the card, close the card and press the box flat.
Open the card and check that the box pops up.
Step 5: Add a Character
Step 6: Add a Cover and Message
Add a message and decorate your card.
Step 7: Did You Know?
Step 8: Try This Next!
Use two or more boxes. Or make several boxes that are different lengths and widths. This lets your characters pop up in different places, like near the front and near the back of the card.