Human-robot interfaces for interacting with hundreds ofautonomous robots must be very different from single-robot interfaces. The central design challenge is developing techniques to maintain, program, and interact with the robots without having to handle them individually. This requires robots that can support hands-free operation, which drives many other aspects of the design. This paper presents the design philosophy and practical experience with human-robot interfaces to develop, debug, and evaluate distributed algorithms on the 112-robot iRobot Swarm. These human-robot interaction (HRI) techniques fall into three categories: a physical infrastructure to support hands-free operation, utility software for centralized development and debugging, and carefully designed lights, sounds and movement that allow the user to interpret the inner workings of groups of robots without having to look away or use special equipment. The end result is a useable Swarm, with develop-run-debug cycle times approaching that of a simulation.