This is one I used for a beginners sling class. Tennis balls are nice safe ammo for beginners to use and are easy to find once you learn to send them a long way.

The pouch is of leather, 8 inches long and 3 inches wide (20cm x 7cm). The slits across the center of the pouch allow the leather to cup itself around the ball. These are made by making holes with a leather punch and cutting between them with a sharp knife to remove a narrow strip.

The cords are of stout jute string from a gardening store, folded in half and reverse twisted by hand so the final cord is two strands thick. It attaches by pushing the folded end through a punched hole in the pouch from the outside, untwisting it and feeding the rest of the cord through the loop.

The cord length is 25 inches (64 cm) each for a final loaded length of 29 inches (75 cm). The release cord has a double overhand knot and the retention cord has a perfection loop.