You'll finish with: A new starter productive on day one.
The quiet payoff. Most of what a new starter needs to learn in their first month is written down in that project already.
Week one, two ways
It doesn't replace training. It removes the part that's just "how we say things here", so your time goes on judgement instead of tone.
A new starter produces something sendable in week one without you rewriting the tone.
No new starter due? You don't have to wait. Read your own "how we work here" file as though you'd never seen the business, and write down every question it leaves you with. Those gaps are the same ones a real new starter will hit.
If you find yourself explaining the same thing to them in week two that the file was supposed to cover, the file describes what you do rather than how you decide. Add the judgement call, not the process step — "we quote fit-outs after a site visit, never over the phone" beats "follow the quoting procedure".
One shared context, one voice, one owner — and new people productive faster because it's all written down.