The trick to this was figuring out what to put on each side so there were the right number of letters and spaces to match the number of penants. I needed "Happy Birthday" and quickly realized it might be more versatile as two separate banners. I came up with a few combinations that would work for the reverse side, but I finally ended up with "Yay" and "Celebrate" and those are generic enough to be used frequently.
Lay your second color of fabric over the Heat N Bond with wrong sides together. Trim it so you have a piece the same size as the other piece. Fuse these together.