So, we have blocked, squared up, and trimmed edges of a quilted piece to be faced rather than bound. I like to run a stabilizing straight stitch just in from the freshly trimmed edges. The sooner the better before loose thread ends begin to emerge from the trimming just completed. BUT... before that, loosen the pressure on your pressure foot. If you leave it in a default setting, you may well stretch out the blocking you just completed. So...loosen up, my friend! :-)
Next... straight stitch just inside the edge. Try to keep it no more than 1/8 inch. Skinny is good!