Really there are two distinct steps to making an open project accessible for participation and contribution.
Community Mindset: Successful pathways begin with a belief and vision that community collaboration is an opportunity.
Designing for Participation: Community matters. Design topics for this step include identifying 'parcels' of work, segment-able pieces, skills, documentation, incentives, and ways to empower emerging leaders.
The goal of this session would be to leave with actionable items for your community, based on an interactive brainstorming session.
- I've run similar sessions at Mozilla and Benetech.