Measure out another piece. Stick it on top of the first strip of tape, placing the top of the second strip at the middle of the first so that it is positioned halfway down.
Continue building your sheet until it is a square, as tall as the width of your paper.
Fold the square in half. I suggest pressing the edge together first, then smoothing back toward the fold. Once you press those sticky sides together, you won't be able to pull them apart, so take your time here.
Repeat this step to make the other side of the billfold. Set these pieces aside for now. Next, we'll make the credit card pockets.