if you are using a 3/8" seam to put the binding on, then stop 3/8" before you get to the corner, take the quilt out and turn it around like you're going to sew the next seam when you flip the binding up make sure you have a good SHARP angle, the outside of the binding should be a straight line with the edge of the quilt, when you lay the binding back down on top of the quilt make sure your folded edge is exactly even with the top edge of the quilt, it's better to be 2-3 threads shorter than longer here, put a pin in it to hold it just like you have then sew her down. when you turn it to the back for the final stitching the folds will open opposite each other