How to grow communities?

Mission. Pick a problem area that is meaningful to you and the world.
People. Approach people who have skills in communication and who have access to networks of people around this problem area. Offer to co-create a community project to realise a mission.
Structure. List why community exists, where and how often it will meet, what community will do.
Tools. Create a calendar for the team to see how often community meets and what needs to be done to get there.