well, it takes me twenty minutes to make a really simple sling that looks nice, and I can sell.  So I sell them in bulk now, and cheap.  I have made nearly fifty pounds from slings.  Most of my slings are made up of cheap braiding rip offs - I don't have the patience to braid, or the skill, so I just wrap the sling in green thread.  Looks alright, even when closely analysed, and holds together well.  The pouch is created by adding extra string and tying it back with thread into two separate parts, so it forms a split pouch cradle thingy.  You then just put the sling on top of the radiator, so that it folds over due the heat, and forms the pocket properly.  Works well, and can shoot large stones.