I'm not aware of any tutorials for African slings, or whether or not anyone has tried to reproduce one, but the American Museum of Natural History has some African slings in their collection. I'm not sure if they were specifically used by shepherds or not, but they might give you some ideas. Here's a link to the AMNH African Anthropology Database:
https://anthro.amnh.org/africa.
Just do a search for "sling" and you should see a few examples.

-Timothy Potter

https://www.youtube.com/watch?v=OxyjspiJiVU

This was posted years ago I think. It looks too familiar.

By the way: Some years ago I read somewhere that a boy had been killed by an elephant after he shot the elephant with a sling...

There was a guy a year or two ago who did have a bunch of African slings posted.
I can remember well enough not to try and find it so here goes:
They were from West Africa and made of natural fibres of some sort.
Essentially they had a  netted pouch with twisted cords and were big and long. Somewhere around 4 feet when folded. The poster went on to say they were handmade by villagers in the area and the models he posted were pretty rustic and roughly made. They also had claims of hitting birds at a distance even though their slings were far from pretty like many of the ones we forum members make.
Walter makes a nice netted sling and uses natural fibers, you might message him for info.