Follow the instructions for the pattern for the continuous flap. Please see bottom note.
Turn in 1/4" seam allowance on one long edge of continuous lap.
With right sides together, pin lap to sleeve, placing remaining 1/4" seamline along stitching.
Stitch. Please see bottom note before doing this.
Press seam toward lap.
Turn pressed edge of lap to inside over seam.
I stitched the right side of the flap so no slipstitching is needed. The directions have you sew it where the flap is turned to the inside of the shirt and slipped stitched.