Apply the first stitch by pulling the needle through the fabric from the back of the pocket-patch but above the base jeans fabric. This will ensure that the knot will be safe between the fabrics when the stitching is complete, and also ensure that the knot will not disturb the skin of the user afterwards.

Keep the stitches close to the edge, ideally along the original seam. The tighter/shorter the stitches, the more stable the mend will be. The easiest stitches would probably be running stitches (just up and down, like a dolphin jumping at the surface of the water), or backstitch (10 mm forward, 5 mm back).