You`ll need cordage in two different colors, a needle for weaving, scissors or a sharp knife, some glue and a “loom” that can be everything that`s flat and hard. I used an amazon envelope made of hard paper, where (for having a good background) a white sheet of paper was attached to.

Take 8 strands of cordage that folded into half have the length of the future pouch + enough length for braiding the cords + some additional 6-8 inches.  Divide your folded strands into two groups and position them over the loom as shown in picture 1.
Turn the loom and the cords around and pull the longer strands of each group through their corresponding loops (2) on the backside of the loom.
Tie the free ends together with a knot (3) and turn around the loom (4). Now you can start weaving.

The result will look like picture 1. The red letters a and b indicate your first woven rows. A brown row followed by a green one above will be called a double-row. 
Weave two double-rows above and two below the first double -row  (2).
In picture 3 there are two more double-rows on each side added.
Now it`s time to tighten the weft by pushing the rows together in the vertical direction. You may hold the corresponding warp cord when you push a part of the weaving away from it to the center.
On picture 4 you can see that the tightened weft formed brown and green stripes.

Now the number of warp-cords is reduced from 8 to 6 by taking the outer warps together as indicated in picture 1.
Continue weaving, always alternating brown and green cords (2) and reduce the width of the pouch by weaving tighter than you did in the center of the pouch (3). After pushing the rows together you`ll observe a change in the stripe-pattern.
Weave until there are 6 double-rows (4)

Again reduce the number of warp-cords, now from 6 to 4, weave again tighter than you did before to reduce the width of the pouch.  Make 6 double-rows on each side.

Repeat the last steps on the other side of the pouch. The picture shows the resulting pouch (again from the ammo-side) with the remaining green weaving strands coming out of the pouch top right and below left.

(1) Now take the other weaving strand(s) below left and start sewing upwards the left border.  If you made the pouch the same way like shown in this tutorial on this (left) side the brown loops should be at the ammo side (=inside) of the pouch. Sew again hiding the bigger parts of the loops.
(2) After you`ve made the knot, the pouch should look like this.
(3) Secure all knots by adding a drop of glue on each one and trim the ends. Here you can form the pouch for a last time by carefully pulling the warp strands, until the pouch gets the desired cupped shape. Then make cuts to open the big loops on each end (release and retention ends) of the pouch. You`ll get now 4 long and 4 short (double-) strands on each side.
The short strands have to be worked into the release and retention cord by braiding or splicing, depending in which way you make the cords. As it`s quicker I made reverse twisted cords and used splicing. The finished sling you can see on picture 4.

Have fun with your new shepherd sling!

Great tutorial, thanks again! I have added it to the FAQ tutorial list.