I think when I made a card that had that look, I just cut an A2 panel. Then I played around with how I wanted it on the card front, as far as the angle and all that. Then you can either adhere it and trim, or flip the card over, mark the outline and trim. If you did that, you'd have a template.
It was the blue layer on
this card. I'm sure I didn't measure a dang thing.
It's hard to come up with measurements because you would need not only lengths of sides, but angles, too: not all of those are right angles, so it's harder to get the trimming right.