After watching two of my students methodically divide a triangular tree and a bowed, gift box into individual triangles on the bulletin board, I had one of my assistants prepare an art project that basically duplicated the triangular tree work.
I stated that the triangles had been cut by hand rather than a machine so some were slightly larger or smaller than others and would need to be trimmed to fit exactly. I watched as the elders did in fact do that. It was amazing to see how at times they trimmed only the tiniest sliver of paper so that the triangles fit perfectly together.
The student that did the chalk work in the picture at the beginning of this post re-created it almost exactly in her art piece, including numbering the triangles - her own idea and decision to do so, none of the other students did.
It was a very successful project. Note that the students did not decorate their trees with drawn ornaments or in fact any illustrations. They used pieces of ribbon, but nothing else. This is a sign that they are maturing as they did not need to add more to their pieces. They were satisfied with them without the embellishments.