The folding instructions are now included within the ODG file on a second page, and I’ve included photos of each step in the folding process. This should help clarify some of the more tricky steps, and show what the final result is intended to look like!
This file is sized for US Letter, but stretching it to print on A4 should work equally well. Further, the lines run right to the edge of the paper, which many printers cannot accommodate; however, on all test printers only a small amount of non-essential information has been lost, which does not harm the plane creation.
Feedback and custom variations are welcome! (This file is licensed CC-BY-SA. Please link to this blog post if you share derivations online.)