Tutorial, part 5 - Fly Onesie

Apply fly interfacing (piece R) to the wrong side of the bottom of the left front fly (piece O). 

Sew the fly binding (piece P) to the front fly along the long straight edge, edges flush and right sides together.

Press the fly binding away from fly.

Turn fly binding under along edge of fly and pin underside of fly binding in place. 

"Stitch in the ditch" along fly/fly binding seam line to secure underside of fly binding.

The fly should look like this:

Remove the excess fly binding by clipping close to the stitch line.

Press fly binding. 

Repeat for other side (except interfacing). 

Overlap the two fly pieces, matching centers, and with both right sides facing outward.

Baste or sew the fly halves together ¼" or so from the top edge where the two halves overlap, matching centers. 

Sew the fly assembly onto the undershirt front, matching centers and side edges.

Apply fly interfacing (piece R) to the wrong side of the bottom of the back onesie.

NEXT: Tutorial, part 6 - Sleeves