need help to make solid imprint of inner shape.  basically its a pentagon compilation from flat plates. i want to weld those together and for that i need to make a mold to i can align plates properly. I was able to design part but now im trying to figure out easiest way to make solid  so i can 3d print it and place parts on it for welding

Welding jig woudl be like kinda a crown like from inner parts form here...

Any ideas?

Worst case i can just design shape based on  and angles