Unflattening design refers to gaining new perspectives on design by considering different viewpoints, constraints, and mental models. Design problems are not flat but rather complex with multiple dimensions that introduce new constraints and opportunities. To overcome the limitations of a flat perspective, designers need to switch between open and closed mindsets, being naive and confident at different stages. Variation in work context, tools, and people can bring new perspectives, while constraints like mobile-first design or random behavioral triggers can also be effective. By zooming in and out, exploring smaller problems within larger systems, and borrowing mental models from others, designers can unflatten their perspectives and create better design decisions. Ultimately, design is a modeling activity that involves defining and sharing mental models with users and colleagues, and constantly pushing to unflatten one's perspective.