Core/Cavity - Boolean Difference? Trying to export exterior faces of a mesh....stumped

Hello World,

I have this small form of rotated panels and I am looking for some help.

I would like to be able to bake or export the exterior faces of the mesh only. I want to use this form to create a small mold however I cannot figure out how to simplify the mesh that I have and export the exterior faces into ideally a surface. I have tried to trim and subtract the mesh from a larger cube but I cant seem to get it to work.

Ideally I would like to have the cylinder capped and bake the exterior faces only, would love a push in the right direction.

Any suggestions or other ideas of how to accomplish this would be super helpful!

QWorking Files _ Stepped (155.0 KB)