HERE, HERE, and HERE, and some other places too (use the labels at the bottom of the blog to find them all) so I'm not going to go over the step-by-step again in this post. Instead, here are links to the handout and PowerPoint that were shared with workshop attendees. They are also shared on the Document Weblinks tab on the upper right of the blog, if viewed in your browser.
I hope it was a worthwhile workshop for everyone there!
I also taught a ticketed hands-on workshop called "The Amazing Flexagon - Magic with Art and Math". I've blogged about this project before several times; HERE's one such link.