I have done mitered corners often. They always come out, BUT. . . .Sometimes it takes me more time to get it right than I think it is worth. So often I just opt not to do them. Here is a video that shows how to make them. It is a little slow going at first, but it was worth my while to stay with it and view the whole thing. I have not tried this technique yet, but I shall soon. In fact I have a quilt top done to the point that I was ready to put on the final border, which I was going to miter. I have had it to this point for several months and have been putting it off. I will let you know how they come out.