I bought the tool a few years ago because I struggled with not having a "bump"--but could never figure out how to use it correctly despite the MSQG video. But I did get great directions in the little booklet that came with a Fons & Porter subscription--which I now use but without all the marking they show.
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Basically,with about a 10" tail overlapping both ends I fold back the ends so there is a 1/4" gap between them(I use a scant 1/4" if it's bias binding as there's a little more stretch) and press. Then I open up those ends and with right sides together, pin so that the pressed line match up to allow me to sew them together just like when you join to 2.5" strips on with a bias seam(you have to "bunch" the quilt a bit to get the binding to meet appropriately). Before I cut the tails I always fold it to make sure I didn't get a twist in it So far this method has always worked for smooth binding.
The binding tool I have used successfully to make a "braided" tabletopper!