You can also go to youtube and search "how to make a slingshot" for example, see what you get:
https://www.youtube....ake a slingshot
Also search "tie attach bands tubes pouch slingshot", this way you get: https://www.youtube....pouch slingshot
Try also other search..
But the people above are completely right, here in the forum you will find lots of information, for example, go mostly after Homemade Slingshots section in this forum, very often people who present their slingshots also do some logs and/or explain the process, sometimes complete process, sometimes something specific to that slingshot like an interesting way of how the wood was stained, new way of attachment etc.
In essence, there are chunks of knowledge that relate to various aspects of slingshots:
history of slingshots;
rubber bands, tubes, rubber features;
harvesting and drying forks;
selecting wood/plywood/ and other types of materials such as micarta (you can search this too) for frames (not natural forks);
carving, cutting, sanding, glueing, drilling etc
staining, painting, protecting (like with Boiled Linseed Oil , BLO or other oils), coating with lacquers, PUR lacquers, decorating... and many other things;
bands/tubes measuring, cutting, attaching to the tips (many different ways), in this regard terms like TTF and OTT (see the pinned threads related to slingshot terms and other stuff at the top of Newbie Question Forum);
pouch designing, cutting and attaching the rubber..
shooting, shooting styles, stances, targets, catch boxes, target shooting, hunting, plinking etc.
types of slingshots, ways to gold slingshot (hammer grip, pinch, thumb support..)
I did not put this to scare you off but that you know whats out there and that you can make a more structural approach to your research into this vast field of knowledge.
The best thing is that you say to yourself: "this's gonna take years.."