All the templates used in the book can be printed out here. Each template is two A4 pages, for the front and back of each flexagon.
There are also a set of blank templates, plus a few extras for even more fun!
Make sure the printer's paper guide isn't loose! Print the front first, then turn the paper over and re-insert it to print the back. Hold the finished sheet up to a light to check the images are aligned. Most printers will do this well enough, but if the pictures don't align, print the fronts and backs on separate sheets. Paste them together (with spray mount is best) then cut them out.