3-D Valentine's Day Accordion Card
Source: Martha Stewart
If planning to mail the card, measure the envelope first and size the card accordingly (usually about 1/4 inch smaller all around). For the cleanest results, cut the paper with a craft knife on a self-healing mat (cut straight lines along a ruler). Some cards need the additional backing to conceal cuts or add weight; create a border by cutting the back piece slightly larger than the base, and layer patterned and solid papers.
Print a template on card stock, cut, and trace onto the paper for the folded piece. (If making one card, print directly on desired paper.)
Fold along score marks. Then unfold, cut out, and refold.
Position the folded piece inside base card so it pops. Secure with double-sided tape.