My first idea was to hold each edge against the other with a collar. The difficulty was to find a core to keep alignement nice an redular. Since I was trying to get a structure as precise as possible to be able to glue paper on it, the tolerances were very slight.

I cut some pentagons in 5mm plywood. It is still to imprecise and difficult to align.

I tried some thermoforming plastic but I've been unable to find the right way to shape it. Molds I tried to make were imprecise and the plastic was not flexible enough to get through a kind of pentagonal syringe I built.

Tapering each contact edge is certainly a good way to go but it seemed difficult to get a precise result on such small parts.

The best results were obtained with 3mm screws.

Since it was difficult to put everything in place while the collar was not tight, I cut some tools to keep each part in place.