I was told to sew it on with a 1/8" seam allowance so that when you sew down the next border with a 1/4" seam allowance, it would cover the previous stitching. Think of it as a basting seam just to hold it in place.
And it does make a nice framing border but, if you are taking it to a long arm quilter, ask first if they will have trouble with a flange border.