Admin → Channel list. Anyone can see it; sort by members and last activity.
Active / dormant (90+ days quiet) / dead. Dead channels get archived, not debated.
Archiving is reversible and preserves history — the fear is misplaced. Do it in bulk, announce it once.
#proj-, #team-, #help-, #social-. New members can navigate without a tour.
New channels need a prefix and an owner. Pin it in #general. Slack stays clean because a rule exists.