With increasing environmental issues, social polarisation, and democratic disconnection, design practice must move from its customary consultation to approaches that constructively develop resilience, inclusion, and ecological stewardship. This article outlines the Ecological Citizen(s) Preferable Futures Deck (PF Deck), a speculative, scenarios-based set of tools co-designed with a UKRI-funded collaboration. Located at the intersection of participatory design, futures thinking, and ecological citizenship, the PF Deck is a well-being intervention that operates through physical, mental, social, and environmental space. In this article, we understand ecological well-being as the capacity of human and more-than-human systems to flourish together within planetary limits, and social well-being as the quality of relationships, inclusion, and justice that enable people and communities to live thriving, dignified, connected lives. It aims to cultivate reflection, conversation, and imagination and to evoke place-based action for individual and collective well-being for an ecologically ethical transition. The PF Deck recognises that human well-being and planetary health are connected. Evidence is repeatedly showing that access to nature, whether in green space, ecological stewardship, or innovations such as green prescribing, enhances physical and mental well-being. Yet, human activity substantially impacts ecological systems with responsibilities extending beyond individuals. The PF Deck responds by offering structured yet open-ended questions that challenge people to think about other possible futures, redefine civic agency, and think about their or their organisations ecological role. Tested through contexts like the London Design Festival, the Royal College of Art, and Falmouth University, the PF Deck has enabled values-based dialogue, systems literacy, and co-design of civic futures that are attuned to social and ecological flourishing. Rather than imposing solutions, it is a relational scaffold that enables pluralism, care, and distributed authorship. We term this a post-participatory intervention: designers do not simply facilitate ‘good’ participation in predefined projects, but act as catalysts and conveners of ongoing, community-led practices that may continue and transform beyond the original design frame. By remapping designers as facilitators of participation rather than makers of results, the PF Deck encourages a post-participatory paradigm grounded in inclusivity, autonomy, and resilience. Theoretically, the paper demonstrates how design interventions can function as an ecology and social well-being mediator. Methodologically, it contributes a postparticipatory design process that combines feminist situated knowledges, ethical language audits, and iterative live testing as an approach to designing for ecological and social well-being. Practically, it offers a piloted toolkit translatable between health, education, community, and policy settings, with particular relevance for; community organisers, educators, civil society organisations, local authorities, and policy-adjacent actors seeking to cultivate ecological citizenship in place-based ways, facilitating community-led ecological and democratic transformation in the midst of climate, health, and social crises.