Board-based software tools for managing collaborative work (e.g. Trello or Microsoft Planner) are highly configurable information systems. Their structure is based on boards that contain cards organized in lists. This structure allows users to organize a wide variety of formal or informal information and work processes in a very flexible way. However, this flexibility means that in every situation the user is required to make decisions to design a new board from scratch, which is not a straightforward task, specially if performed by non-technical users. In this paper, we carried out a study following an inductive approach consisting of analyzing 91 Trello board designs from both research works and board templates proposed by Trello users, which cover a wide variety of domains and use cases. The result is twofold. First, we propose a metamodel for designing boards that takes into account not only the structure of the board but also other decisions like the type of information cards manage and behavioural aspects of how cards flow. Second, we use this metamodel to identify and characterize 8 patterns that are commonly used in board designs. These results, applicable to all board-based tools, provide insights that can be useful for users to design solutions more effectively and efficiently and help us to better understand the roles that these information systems may play in the current enterprise information systems ecosystem.