We describe four design principles that guide the Mosaic Fellows Program at Indiana University, a program focused on supporting faculty pedagogy in active learning spaces. The design principles focus on exploring a variety of classrooms with faculty Fellows, engaging Fellows' individual goals, creating shared learning experiences, and encouraging Fellows to share their insights with a larger university audience to support institutional change. We discuss each design principle in turn, explaining the rationale behind the principle, and then give specific examples of the design principle in practice. We conclude with implications for faculty development about active learning spaces at other institutions.