Merry Christmas, all.
Small problem: sewing is going to be with right sides together, so that reverses the curves. The pocket flap interfacing is cut a 1/4" shorter than the outer material, which acts a as handy measure. The trick is to go slow and check measurements often.
All that is left is to back-stitch the bag sides, and buttonhole stitch the edges of the slit to the back of the pocket. A bit of top stitching to finish the flap and four decorative buttons complete things. One down, one to go.