Say that fast three times--HA! I have Diana Gibbs to thank for this technique. It looks really hard, but it's very easy and creates such a cool effect that it can be the main element of the card.
This is harder to explain than it is to execute, but I'll do my best to make it simple. Take a 1"x12" strip of Designer Series Paper and score it at .75" and 1" the length of the strip. This will give you more pleats than will fit on the card, but it's better to have more than you need. After you have the length scored, hold your strip vertically in your hand. Fold the 1" score, which will be your 2nd score, back over the top of the .75" score. Go to the next score line and fold it down over the top of the 1" score. This will create your first pleat. Continue this the length of the strip, and you will end up with 5 or 6 pleats.
Now center four of the pleats along the length of the card base, which is 5.5"x4.25". Run strips of adhesive along the valleys of the pleats and adhere to the card base or matting. You will have excess to trim from the edges. The matting measurements are 1.75"x5.5". Mine was done in Whisper White to contrast with the red pattern from the Twitterpated pack of DSP.
I layered the Whisper White mat on top of a piece of Riding Hood Red that measures 3"x5.5". The DSP that's adhered to the base of the card measures 4 1/8"x5.5". The base is Island Indigo, which coordinates with the blue in the DSP.
The greeting comes from the Apothecary Art stamp set I've been featuring this week. It comes in clear and wood mount, and I like the clear mount option for being able to position the stamps. There are two greetings in the set, Happiest Birthday and So Grateful: two sentiments that are very useful, as the majority of cards needed are either birthday or thank you! I stamped it in Riding Hood Red on a scrap of card stock. I punched a hole in it and threaded 1/8" Whisper White ribbon through it and through the first pleat. I neat bow secures it.
I encourage you to give this technique a try. If you encounter any problems, feel free to leave a comment and I'll try to help.