Convert Flat Box into Closed Curve? Or another method for creating a 2D bounding box?

So I can create a Bounding Box out of 2D curves, and it outputs as Flat Boxes. What can I do with those? I’d like resulting closed curves I can offset.

Fantastic, I should have thought about that rather than trying a curve. I also had the plane wrong, so my rectangles were becoming lines at first.