There is an old joke about woodworkers that has a hundred variations but goes something like this: Someone asks another person how long it will take for a woodworker to make the cut he needs to make.
The second person replies that it will take five seconds to make the cut, but five days to make the jig first. While this is obviously an exaggeration, time spent making jigs is important, and you should build jigs whenever you can.
A jig is just an item that helps you complete a woodworking process with much more accuracy than without. For example, a simple block of wood that is clamped to a board to help you saw straighter is a kind of jig.
On the more complex side, a sliding box that makes it easier to cut 90-degree angles on the table saw is also a jig.
While you can do most of the things without the jig, the process is a lot harder, and the results are a lot less uniform. The whole point of the guitar-making ideas is to make the process easier, more accurate, and repeatable.
Especially if you are planning on making several of the same things, jigs and assisting devices that you make will only make your process much easier, more enjoyable, and much more uniform on the end.
If you need some help finding jigs for the type of woodworking that you are interested in doing, look online at what other people are making, and spend one time studying their setups.