Many people know how to compromise existing systems, and capture-the-flag contests are increasing this number. There is a dearth of people who know how to design and build secure systems. A collaborative contest to build secure systems to meet specific goals—a “make-the-flag” exercise—could encourage more people to participate in cybersecurity exercises, and learn how to design and build secure systems. This paper presents a generic design for such an exercise. It explores the goals, organization, constraints, and rules. It also discusses preparations and how to run the exercise and evaluate the results. Several variations are also presented.