Vacuum bagging is a commonly used technique in composites, and for good reason. When done correctly, your part will have a nice, uniformly distributed compression about the surface of the layup. This in turn helps to minimize any voids (e.g. bubbles and wrinkles) in the buildup of layers. Also, when used with a porous substrate made of peel-ply and breather-cloth as we'll see, it assists in having the optimal ratio of resin to reinforcement (e.g fiberglass, or carbon fiber) by squeezing out the excess.
The project is quite simple for illustrative purposes. I'm making a small container from a mold of a nice tea container lid. I'll go over the steps to make this part, but the vacuum bagging phase is what this topic is about, so we'll be delving into that a bit more thoroughly.