The potential of blockchain for the supply chain sector is widely acknowledged, but it is not always clear how this potential can be realized in specific use cases. Supply chain blockchains must fit into the wider context of complex business relationships, existing technical systems, and ever-changing requirements. Consequently, their design requires a holistic approach which appreciates the complex interplay between the technology and its context. This paper presents a corresponding framework for analyzing and designing blockchain systems in the supply chain sector. It outlines the benefits of blockchain technology, provides guidance on deriving requirements from the use case, and distills critical implementation features.