These are the slides from the LIBER 2021 Session Powering Sustainable Open Publishing Platforms. This session will be chaired by Charlotte Wien, University Library of Southern Denmark Mapping the OA Diamond landscape worldwide. Towards a more sustainable future, Vanessa Proudman, SPARC Europe New University Press: collaborative innovation in Diamond Scientific Publishing, Natalia Grygierczyk, Radboud University, the Netherlands An Open Book: launching a library-based open access books hosting service, Rebecca Wojturska, University of Edinburgh, United Kingdom This session is all about the future of Open Publishing. Are you interested in hearing about challenges and opportunities for Diamond Open Access, or would you like to learn about the book-hosting service single-handedly launched and operated by a university library? Then please go ahead and sign up for this session! Vanessa Proudman presents the results of ‘The Diamond Open Access Study’, a research study commissioned by cOAlition S. In her presentation, a new understanding of the OA Diamond sector and its maturity with respect to editorial quality assurance practices and Plan S technical requirements will be shared. Additionally, she will discuss key perceived challenges of OA Diamond journal editors and the current financial sustainability of the sector. Most importantly, she will be presenting the new OA publishing Commons, which seeks to bring together the world’s community-driven/governed journals and platforms, connect them and technically support them in a new, increasingly coordinated and sustainable way. Next, Natalia Grygierczyk discusses an innovative model for Diamond Open Access scientific publishing, explaining not just its theoretical foundations, but also how it is actually implemented in the newly started OA Radboud University Press (OA RUP). Within the new cooperative model, the OA RUP aims to enable, guide, and support academic editorial boards in the transition process to Diamond Open Access. This presentation provides an overview of the new publishing model, its operational activities, and financial aspects. It concretely describes the collaborative process with various service providers, how the OA RUP is financially sustainable in the long term and how cost-effectiveness is achieved in the transition to Open Access. Finally, Rebecca Wojturska provides insight into the world of launching a library-based Open Access book-hosting service. The presentation will reflect on the timeline, successes and learning points of the current University of Edinburgh library project and provide recommendations and conclusions to attendees. It will also discuss how to grow a book-hosting service and how it is useful in supporting teaching and learning. Finally, it will consider the technical requirements of such a project and share anecdotal evidence from academic and student users to document the successes of the University of Edinburgh library project and launch. As such, the primary audience for this presentation is the librarian who is beginning their own book-hosting service, or who is considering it, as well as those interested in Open Access publishing.