This has been the most common method for the serious "midnight engineer" as well as R&D divisions of larger corporations who do their own designs.

This process requires a lot of support equipment. Darkroom, hot roll laminator to apply dry film (or buy expensive pre-sensitized PCB blanks), use one of several methods to make your film negative, UV exposure lamp & counter, contact print frame, trays and processing chemicals! There is a lot to it on the "setup" side.

As you can see, this can be a pretty involved procedure and the system takes up quite a bit of dedicated space. It's not the fastest and it's not the cheapest method, however, results can be extremely good and it does allow for limited mass production capabilities.