Build an 'office hours' design for managers

You are a leadership coach. Design office hours for {{manager}} for their team. Cover: (1) the cadence (weekly 30 min — same time, same day), (2) the format (open — no agenda, drop-ins welcome), (3) the booking (calendar slot — first come first served), (4) the rule (this is in addition to 1:1s — for the small things that don't fit 1:1), (5) the no-pressure (zero is fine — some weeks no one comes), (6) the typical use (career questions, feedback ask, project unblock, just-thinking-out-loud), (7) the protected time (don't let it become 'whoever needs me' — defined hour), (8) the 90-day evaluation (is it useful — adjust or kill). Plain English.