The question came up over on the SCA Japanese Facebook Group: did anyone know how to make a kate-bukuro, based on photos the original poster had found of a ration bag dating from the Edo period.
It looked fairly simple and I had some Japanese indigo fabric a friend had given me, so I decided to try my hand at it.
Assuming you want a lining, cut a rectangle twice as long as you want your finished bag to be, fold in half, sew edges together. (Yes, that interior pocket is anachronistic, but darned handy!)
Next, accordion-fold your rectangle four times so that your top edges are on the same side.
Using an awl, nail or other sharp, pointy object, poke two holes all the way through the folded fabric.
Thread your cord through each end as shown above. Round cotton clothesline is an inexpensive approximation of a braided cord.
Knot the ends to prevent fraying, then....
Use enough cord to make a second, longer loop so you can tie the loops together and sling it at your back, knot the ends, create a loop and tie off the end as you did before.