First you need to measure the backs of the chairs you plan to put the envelopes on, and decide how big you want your envelopes to be. My chairs are pretty standard, and I decided to use a piece of 8 1/2 x 11 paper for my template.
1. Start with three pieces of card stock and label them with a number 1, 2, and 3.
5. You can use the discarded piece of your #2 to make your heart template:
6. Trace your heart template on a folded piece of red felt and cut out your hearts.
11. Stitch over those lines on piece #3. (Notice I don't go all the way to the corners, so they'll match up with all of the seams.)
12. Now cut your ribbon: You'll need two pieces both 47 inches long. Seal the cut pieces of your ribbon over a candle flame to prevent fraying. You'll need to figure out how your ribbon will fit on your envelope, by seeing how long of ribbon you'll need on each side to hang over your chair. I left 13 inches of ribbon on one side from the bottom, and 25 1/2 inches from the top of the envelope. Place your ribbon 1 1/4 inches from the edges of your envelope (piece #1) and pin. Do both sides.
14. Place your #3 piece on top of the back of the envelope (#1), and pin. Then stitch around it. It is the bottom piece. (Please ignore my bobbin malfunction in the top right of the picture below - I was too lazy to fix it, plus no one will see it...)