> if you make the larger pentagon a plane using the planar tool
> then boolean subtract the inner line

Hi Tim, this was definitely the right idea - just one tip I'd add is that you can select both the outside and the inner curves when you run Planar (or Extrude directly), and that will let you skip the boolean step.

Planar and extrude both can process multiple curves in one go, they know how to make cavities or holes for inner nested loops.

- Michael