At about 12 inch from either end make an additional line across the back for the kettle or catch stitch.
Remove the basting, trim the edges of the patch, press the patch on the wrong side and catch stitch to the garment.
“Kettle stitch,” catch stitch formed in sewing at the head and tail.
This herringbone or catch stitch can be used in many places.
If one wishes, the bag can be decorated with a catch stitch.