Design (thinking) is increasingly considered a promising approach for addressing societal challenges. However, designing for societal transitions, such as the energy transition, requires new approaches to involve non-designers in the design process. Involving the full range of stakeholders affected by a societal transition means inviting perspectives from both the lifeworld, representing private and public spheres, and the system, representing the state and economy, which is not straightforward. The current work elaborates on genuine participation when co-designing for transitions and proposes eight co-design approaches for genuine lifeworld and system participation. These approaches were developed and tested during a six-month study on youth participation in the energy transition, using Frame Creation practices as a substructure. Building on the empirical insights, we reflect on our methodology, challenges encountered, and opportunities for further developing genuine participatory approaches to designing for societal transitions.