The aim of this study is to explore the practical application of Lean with Six Sigma and Agile to create a powerful, synergetic and novel process improvement (PI) method. Going beyond the traditional definitions of Lean, we establish a Factory Physics view of PI which doesn't technically discriminate Lean from non-Lean. We apply a design science approach to help a global bank deploy a continuous process improvement program. By reviewing the literature on PI, we recognize Lean additives viz., Lean Six Sigma and Lean Agile, when synergized, help overcome the limitations of individual PI practices. Our design takes its roots from Factory Physics (FP) and emerges as a novel model synthesizing the theoretical lens of FP with Lean additives for field application. Besides the design of ‘Lean Additives Program’, we deployed the model in several iterations, and studied its performance over a three-year period. The improved system exhibited high levels of efficiency and effectiveness. The longitudinal case evidence demonstrates that Lean additives offer both operational and strategic benefits in firms. © 2021 Elsevier Ltd