Just add the leather pouch and the 2 Rubber tubes, assemble it as shown on the second picture, that's it!
...For the Personal Factory, follow these simple steps:
1- Download the file;
2- Make 3 extra copies of it;
3- in each one of the copies, keep the original at all times, delete somew parts:
3a- First the add-ons, keeping the Slingshot; save it as part 1
3b- Then, on another copy, delete the Slingshot, and the pouch add-ons, and one of the Slingshot add-on, keeping just the other, save it as Part 2,
3c- Then on the last copy, delete all but one of the pouch pieces, save it as Part 3.
Thẽn you manufacture each part, Slingshot 1 time, the other parts 2 times, or more, for spares.