This walkthrough is a detailed narration of what we see in Apple's Watch Craftsmanship videos. Of course, we only get to see a mere fraction of the process; I've tried to provide plausible explanations for the likely steps taking place between the processes shown on film, but these are assumptions and are included only to provide a more satisfying and complete narration.

If you haven't seen the production video's of the Apple Watch, go and enjoy them now. Read this amazing post of Greg Koenig afterwards.