Episciences is a publishing platform for diamond open access overlay journals. The ambition is to provide scientific communities with the technical means to produce high-quality, cost-effective journals in line with FAIR principles. The publication process is based on open repositories (arXiv; Zenodo; HAL). All the published content of a journal is hosted on repositories. Episciences is therefore set up as a service layer for repositories, using them as input and output for open access publication. Episciences is included in the EOSC Marketplace and the OpenAIRE Catalogue. It is interoperable with several OpenAIRE services. This interoperability has enabled us to create new workflows to add post-publication enrichment to our metadata with services such as OpenAIRE Graph, ScholeXplorer, OpenCitations and OpenAIRE Provide. The result of this process is an improvement in the FAIR aspects of our published articles and a better basis for integrating other services such as Open Science Lens (OSL) Page Enhancer.