After seeing this pouch design the first time 3years ago I got the impression that the lines of force in tension would tend to pull the sides together, hence the payload needs to be relatively small. I have not tried the design but other makers like the method.  Zorrro said the tutorial is for method only; the design is up to the individual.

tom

You could try and wing it. Draw out a pouch and add an inch or two to fold over the sides. You cut slits at the edges to help it wrap around the angles.