Thank you for your replies!
Unfortunately I didn't take any pictures so I have to make another pouch.
I will make a tutorial as soon as I have time. Although it may take some days until I find half a day to sit down and make some good pictures.
A short sketch of the construction is nearly finished. I will upload it this week.
@squirrelslinger: Yes, this pouch suits better for spherical stones and not glandes. The width of this pouch is 3 cm, so rather small. I would not take bigger ammo than this. But it is possible to make larger pouches. At the moment I'm making a bag with around 25 cm diameter, 35 cm high with the same technique. Although here you have to add further radial strings to make it stable and dense enough
@Pikaru: Peruvian braids, that's one thing I have not tried yet. I fear that with this string it would get quite thick as you need 24 parallel cords or am I wrong? Thank you also for encouraging me to take time. You are right, the ideas are floating towards me

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@xxxkid123: I like the idea to weave the transition, like first with 6 warps and then bundle them to make a smooth transition to the string.
Could you give me some samples of the loop braid you suggested? I also have no experience with this.
@Rat Man: I will certainly do a little whippings over the critical points. Although I don't think that I could just cut the loops as you did. Polyester is way more slippery than jute. Thank you also for pointing out this tutorial! I was not aware of it.