Su: I am a total newbie at miters, as a matter of fact the one on my medallion was the first one. I Googled it and found a great tut explaining the process. The one I used was the one where you attach the border, stop sewing at .25 inch from the corner and then sew a 45 degree angle. It worked perfectly for me. I think I would always join the borders together before I mitered the corners, it makes it easy to prevent wavy borders plus you only have to miter one time on each corner. Absolutely love what you've done so far!