Fold ends down with right sides together to determine where you'll need to sew them together.

Mark your seam on the wrong side and pin into place.  

Sew along the line.  Trim loose ends to 1/4", and press open.  If necessary, trim corners of seam allowance so they don't poke out on the front.  Pin binding into place. 

Sew remaining opening, beginning and ending with a few backstitches.