Mass customization (MC) manufacturing requires high flexibility to respond to customer needs in a timely manner. Lean manufacturing principles can be easily applied to situations with low levels of MC. However, as the degree of customization increases and customer involvement occurs earlier in the design and fabrication stages, the direct application of lean principles to maintain flow and low levels of inventory becomes difficult. This paper presents a framework to show how other strategies such as Quick Response manufacturing/POLCA, Theory of Constraints, Flexible/Reconfigurable Manufacturing Systems, etc. can be integrated with lean in MC environments. A case study of boat mass customizer is then used to demonstrate how their operations are transformed by for more efficient MC. Simulation models are used to compare pre- and post-improvement performance.