This is one type of atomic arrangement crystal structure: the hexagonal close-packed structure.

Since I'd only ever seen hexagonal prism models in common educational materials, I designed this one to unfold into three separate parts.

Truthfully, I didn't intend to divide it into three parts from the start. After making a “common” hexagonal prism model, removing the support structures proved incredibly tedious!
To make support removal easier, I began considering division. Since I was dividing it anyway, I thought splitting it into three rhombus-shaped parts representing the unit cell might better aid student understanding, so I decided to divide it.
However, simply splitting it into three parts could lead students to get the orientation wrong. And above all, in a school setting, it's common for parts to get separated and lost.
Therefore, I connected them with hinges. This allows it to form the common hexagonal prism shape, while also letting students see that the same structure repeats in the three sections.
The hinges at the unfolded sections connect sharp angles, so figuring out the structure for those parts was the most challenging.
Ideally, if I could have achieved a shape where the sharp angles truly meet, I believe it could have unfolded more effectively. However, with my current ideas, this was the limit. If you have any good ideas, please let me know!

I would be very happy if this work proves useful to you all.