It is from the same book that I have mentioned Strolling Along Paths of Green, , by Yoko Saito.
In the book she recommends that you make a practice copy out of muslin or just plain fabric to get the hang of how the bag is sewn, since it is not a typical construction method.
This is a good idea. It was a little tricky, but it wasn't hard. I think it could be tweaked to make bags in different sizes.
This show a water bottle on to so you can get a sense of the scale,
And here it is folded up, so it could be taken shopping!
this handbag stuff is sort of addictive.