I used a tissue box but cereal boxes, snack boxes or any small cardboard box will work and various sizes make a more interesting project.
Craft foam sheets were used for all of the details.
Fiskars also makes a deep cut craft punch now that's great for materials like cork, metal and thick cardstock. I bought heart shaped craft punches that work fantastic on the foam sheets.
Be creative and turn your Valentine's card box into a mythical creature like a griffin, centaur or mermaid!