Start with a small card (I cut a rectangle from a piece of card stock and folded it in half). Decorate the outside of the card (I didn't do that for this demo, to keep it simple). Cut a skinny rectangle (about 8.5 by 2.5 inches) from a lighter-weight piece of paper; I used construction paper.
My final flap was a bit too wide, so I trimmed it. No biggie.
Now, add letters! I used my fun alphabet stamps, but of course you can hand-write 'em. Starting with the third or fourth panel, stamp/write the letters of your first word on every other panel.
Add glue to the flap that's now on top, and carefully close the card. Press for several seconds to adhere.