Take the outer piece you set aside earlier. Now you want to decide which part will be the “top” (the side you’ll see when the book is sitting on your desk) of the checkbook exterior once you fold it in half. Embroider as desired (I originally wanted to do initials, but I was too lazy to). Take care in accounting for the 1/2-inch seams and 1/8-inch top-stitching when positioning your embroidery.
Pin right sides together with the inside piece. Make sure you orient the exterior piece so that the top part of the exterior faces the transaction pocket part of the lining. Sew along all four sides with slightly more than 1/4-inch seam allowance to hide all the basting stitches. Don’t forget to leave a gap for turning! I usually put the gap at the one of the shorter edges. Turn right side out and press.
This is what it should look like. You can see how our optional holding pieces from Step 5 will work.
Now is the time to check the fit of the cover with your checkbook stuff. Upon putting it in, you want at least 1/4-inch space of horizontal wiggle room to accommodate the top-stitching.
If you have too much excess wiggle room, flip the cover inside out again and stitch around with a up to 1/2-inch seam allowance. I had some variation when I made mine—the first one used a 1/2-inch seam allowance and it turned out perfect. The second required a 1/4-inch seam allowance along the length (8-inch direction) but could still use a 1/2-inch seam allowance along the width (7-inch direction).
Once you’re happy with the fit, clip the corners and trim the seams to reduce bulk.