Control that one relay, put very specific filters on it that boots any spammers from it. Put a limit to how many notes a nsec can make to that relay, when they hit the limit, they get a message to add a new relay to continue posting. Have specific users from the welcome crew with unlimited note creation to welcome new users, answer questions, and can specifically watch for spammers that may have slipped the filters. This could actually also reduce new spammers from the overall protocol if they were booted from the intro relay before adding new relays.