After several decades of evolving, Open Access (OA) publishing is now at the centre of scientific communication, providing access to scientific publications without barriers. In Diamond Open Access, authors can publish free of charge as the institutional sector with universities, research institutions or libraries provide the necessary technological infrastructure. While the commercial model of Open Access dominates in anglophone journals from the Global North, the Diamond OA model shows a much higher level of diversity and origin. However, the Diamond OA landscape continues to be fragmented, is often underfunded, and is not always technically proficient enough to develop its full potential for science and society. The CRAFT-OA project aims to consolidate the Diamond OA publishing landscape. The project focuses on four threads of activities to improve the technical and organisational infrastructure of Diamond OA: (1) Provide technical improvements for journal platforms and journal software (2) Build communities of practice to foster overall infrastructure improvement (3) Increase visibility, discoverability and recognition for Diamond OA publishing (4) Integrate Diamond OA publishing with EOSC and other large-scale data aggregators. CRAFT-OA’s 23 consortium partners from 17 European countries are all engaged in institutional publishing and its infrastructures, and committed to sustaining and developing capacities in the field. Many CRAFT-OA partners are leading organisations at national and European levels in terms of open publishing, and represent internationally visible centres of expertise in Open Science and FAIR implementation with strong connections to EOSC. Within 36 months, CRAFT-OA will deliver technical and community tools, training events, training materials, information, and services for the Diamond OA institutional publishing environment. It will foster communities of practice with the capacity to sustain the project improvements over time.