When I turn a seam like that, I do some pressing before I turn it right-side out. After stitching around the edge (leaving a space to turn) place runner with top facing up and backing down on ironing board. Separate the seam allowances and run iron on top of backing SA, pressing the top SA back on itself. You may have to trim point to get it to lay flat. Be sure to press SA of turning space back, too.(placing an old envelope to act as a guile keeps th section straight) Then when you turn it inside out, you are working with on pressed seam that will lay flat and when sewing turningspace you will have a straight fold to work with.
I must add that I only use flannel or a Good weight cotton as batting in TRs and treat that as part of the backing fabric.
Last edited by bobquilt3; 04-14-2013 at 08:29 AM.