I prefer to use the "Magic Triangle." This was just something new. Marci Baker also has a video on mitered corners that I really like. Sew to within a 1/4" of end, pivot and sew to the "point" then lift the binding, create the mitered corner as usual https://www.youtube.com/watch?v=Vci9-li3aYU

I tend to grab any bag near me that has handles and put one under my machine. then binding in the bag.