Cut outside and lining fabrics 12" x 22" Cut the Heat n bond 11" x 21". Following the fusing instructions on the package, iron the shiny side to the wrong side of the lining, leaving a half inch margin of fabric all the way around the piece. Peel the paper backing from the Heat n Bond, place on wrong side of main fabric and fuse.
Stitch a 1" hem on the 22" end. Fold in half with right sides together and sew the bottom and side seam to make the bag.
Open up bag and 'box' the bottom as shown, the side seam will now be down the back. Using a ruler with a 45 degree line on it, measure in 2.5" from the corners. Click the image to zoom in, I've drawn a red rectangle around the corner measurement to help explain this step. Draw a stitching line.