Learn how to join the ends of binding on your quilts with Bonnie Browning.
The key is to fold the triangle away from you; the fold should be closest to your body. Pin along the fold line, which is your seam line, to double-check the binding. Sew on the fold line. Press the seam open to reduce bulk, then trim the seam to 1/4". Refold the binding and stitch to the edge of your quilt. Viola! it fits perfectly. (This tip was taped on the June 6, 2018 AQS QuiltChat.)
Learn more with Bonnie's Let's Quilt series here: https://www.americanquilter.com/lets-quilt-home