Use 1″ PVC pipe with “T” joints to make a larger bottom heptagon (7 sides) and a smaller version for top. Cut PVC pipe to connect smaller heptagon top to larger bottom (as you can see I ran out of pieces of PVC, so I added an extra unused “T”. This can work by adding a variety of couplers etc., if you run short too. I also covered it entirely with boxing tape once I was sure the shape was correct since I’ve had issues with PVC glue in the past.