I always iron my binding in half. I cut my binding 2 1/2 inches and sew it to the back. Then when I get to the corners I iron them down in a pretty miter. Use my clover clips in 3 places. In the middle of the corner and then one on each side about 4 inches out.
Then if I've used the piped method I'll stitch in the ditch up against the outer binding. But I never pin the entire binding down. Never have a problem with it bunching up at the end.
I love the way it looks crisp and lays so flat.