Please note the following correction:
Step 11.5 (between steps 11 and 12, in the PIECE THE FRONT AND BACK section): Press the two panels with a hot steam iron so they lay flat. Use a seam ripper to remove all the basting stitches. NOTE: Do not cut the basting stitches; pull them out one by one. You should be able to pull the knot in each basting thread and remove the last couple stitches easily. When all the basting is removed, pop out the card stock templates. (You can reuse these for another project if you'd like.) Press the panels again so all the seam allowances are laying flat.