Fold to create pleats as shown in the photo below. Once you have completed this process, repeat using your second 2 x 12 strip. You will then be able to connect the two so you have enought to create a 2 x 12 pleated strip.
I hope you give this technique a try. You will love the look it adds to your pages without adding bulk. This is perfect if you plan to design a page for a scrapbook.