this resembles the kind of slings shepards make here in the south of Spain (and the same i've seen in Balear Islands) iit's very simple easy and quick to make
Last one i've done is nylon 5mm just need 3 cords of aprox. 6 to 7 meter.
start in the middle making 3 srand braid for the finger ring.
once you 've got the apropriate size, join the 6 strings and start 3 strand braid for the retention cord (each strand with 2 strings) once you get the desired lenght divide the strings and braid two separate 3 strands braids (each strand with 1 string) to the lenght of the desired pouch.
Then join the 6 strings again and start to braid 3 strand braid (again 2 string per strand) to make the release cord to the desired leght.
it's desirable to free and trim some of the string fibers at the end of the release cord, so it gets thinner like a latigo and if you let some fibers free at the end(about 4 inches or so) it will make a crack sound like a latigo. (this is useful for shepards cause sheep doing something wrong i.e. eating some forbidden plant/tree or getting too far from the flock, only hearing the crack sound stop doing that wrong and behaves properly
)