Here's my first attempt at a simple model using paracord. The sling is about 4 ft long from loop to knot, the pouch is about 5 inches long and done in a weave with three warps. It looks a bit uneven since I made the weave loose, so it would conform somewhat to what I put in it. It's shown with a 3/4 inch ball bearing.
Here's another photo, this one showing how I made the three warps in the center of the 6 foot length of paracord, which I used for the main holding/release cord. I just made a short loop about halfway down the cord, tied an over hand knot around the standing end, the working end comes down the center of the loop, another overhand knot is tied with the working end going away from the loop. I didn't measure the cord I used for the weave, but figure to use about a foot of paracord per inch of weave plus some extra to be safe.
I ran the starting end of the weft(weaving cord) thru one of the overhand knots to keep it out of the way. when I finished, I tucked the paracord ends down the center of the weave on each end.
You can find lots of information abouts slings and slinging, at Slinging.org.