This article draws on doctoral research into conferences for teacher professional learning and development (PLD). It outlines the literature on teacher PLD, and describes the process by which the collective, game-like activity, Plan D, was designed and prototyped. Plan D affords teachers the opportunity to design their own, bespoke, PLD experience: a “d.conference’. The emerging findings from the research suggest that Plan D can support teachers to design PLD that interrupts “business as usual” (BAU), taken-for-granted assumptions about how to plan PLD for colleagues. Further, the research suggests that Plan D interrupts BAU through creating four conditions for collective knowledge co-creation, or knowledge-ing. These four conditions are: being purposeful; being open-ended; offering opportunities to play; and offering time and space. Designing effective PLD is emergent from, and contingent on, positive school culture and group dynamics.