User Carpespasm at Instructables.com has posted a nice illustrated “how to,” on making a pair of geta. For dimensions, they suggest using japanesegeta.com’s own geta dimension calculator.
My only suggestion is to string the main strap through a small loop between the toes. I’ll post a photo soon.

Make Your Own Geta Sandles - More DIY How [...]

Video of a Geta Maker

February 2nd, 2009

Sorry for the long absence…
This well produced video was made at the Gujo Odori dance festival in Gujo Hachiman city in Gifu Prefecture. Starting at about 2:00 you can watch the straps being attached to a pair of geta. I’ve seen it done a dozen times, and I still can’t tie the knots correctly.
Thanks to [...]