It was a little tricky to get done. The paper tended to curl up on itself a lot. But it wasn't anything aggressively difficult to do.
It's small hex twists on one side. Open back triangle twists on the other.
I found it most productive to move back and forth between the front and the back. When you begin to get those hex twists working it creates the veins around the triangles. Rather than just focusing on flattening the triangles, I used the veins to help ease everything into place.