I actually did it...and did it right the first time. I used the regular technique as on a 90 degree angle and adjusted the folds as needed.
But...the BEST part is that I created a template.
I have that thin plastic that you can use to make templates and made my own little piece for marking the pin points.
When I get to close to the corner, I lay my template down and match up the edges, then put a pencil mark through the holes.
Remove the template and I know exactly where to stop.
This is a rough template, but after using it on my table topper, I found it VERY helpful.