Step 2: Tape the base together
Cut two lengths about 3" to 3.5" long. Fold them in half long ways and then cut them into triangles. (see the picture). Then tape these to the short sides of the smaller sheet. Then tape the long side of the small sheet with the smaller sides of the triangles to the large sheet at the fold between the two larger sections.
Then finally tape the free sides of the triangles (in orange) to the middle section of the big sheet so that you get a pocket big enough for money.
This sounds confusing but I think the pictures make it relatively clear.