Not only did she sew the straight seam, but she never pressed it open. At that point there are at least 21 layers of fabric at that spot. Three for the back, batt and top (with perhaps a seam or two extra from that), then three layers of doubled over binding with two layers of seam for each layer of binding. A good way to break a needle, and that would not look very nice.
That video may be old, as there are other videos that show how to sew the two binding ends together on the bias. It's really quite simple and easy once you do it a few times.
I press a triangle at the beginning of the binding, and when I get around to the end, I cut the last binding tail exactly even with the bottom of the triangle. The binding is now overlapping just as much as the binding is wide. No matter how wide your binding is, that measurement is always correct. Pick up those two ends, place them right sides together, twist them so that they are at right angles to each other, and sew on that line from one corner to the other.
Press that seam open (finger pressing is OK here) and you should see a square. Now trim the extra triangles off that square, fold it back the way it belongs making sure the seam stays open, and your binding lays perfectly flat.
Last edited by maviskw; 03-15-2016 at 04:48 PM.