You have to do a little more layout, but here is what I do:
I wish I would have check back before I started my gas tank project. I just finished it they day after you posted this. I didn't have any binding materials on hand and was antsy to get it done so I just did the french seam again, but sewing it like that in all those tight corners (which on something that small is as if it's nothing but tight corners) was a slow going pain in the behind.
I'll definitely try to remember this technique for my next project.