I added strips of DSP to the box bottom. Two strips of 1-3/4" x 5-3/4" and two strips of 1-3/4" x 4-1/4".
Put the cards in the box so that the cupcake shows through. I angled my cut-out to mimic the same angle as the cards. As you can see in the very top photo, I added a strip of Rich Razzleberry Polka Dot Grosgrain Ribbon around the box adhering it with Sticky Strip.