Lay the main piece of fabric out with wrong side facing up.
Fold the edges over 1/2 inch, and press all the way around.
Fold the edges over 1/2 inch again, and press all the way around.
Sew 1/2 inch top stitch around the two short sides and one long side, creating a hem on three sides and leaving one long side. We are leaving this part open because we will be sewing in the straps and boning.
Lay the main piece of fabric out on a work surface, and fold it in half to find the middle of that long, unfinished side.
From the middle, measure over 7 inches and mark (I used a pin). This is for the boning.
Tuck the strap under the open hem just outside the mark you made for the boning.
One side tuck in the short strap with the D rings, and on the other side the long strap. Pin in place.
Sew all the way down the long side of the main piece, catching the straps.
Important: Right before you get to the end of the 14 inch section that is for the boning, you will want to start and stop your stitching and leave about a centimeter gap. This is where you will be putting the boning in later. I like to do this by sewing almost all the way to the longer strap, back and fourth stitch, move my needle a centimeter, and then continue to sew (do a back and forth stitch when starting again). Then sew the rest of the way down.