Here is a quick, fun & simple project I made to hold my cards.
I used My Mind's Eye Quite Contrary Little Boy Blue "Curious" Who Loves You two-sided patterned paper.
I cut it out on my Cricut Machine using the CTMH's Artiste cartridge at 6" like the book suggested. You need two sheets of paper to make this project because it is just a bit bigger than 6 inches when it cuts it out.
This is the largest size of card holder that you can make using a 12 x 12 mat. It fits a 4 1/4 x 5 1/2 vertical card quite nicely and I can put 7 embellished cards in one holder without squishing them.