Discrete event simulation is a useful tool for optimizing complex systems in an environment with process variability. One such system is layout planning for a new manufacturing facility.  However, creating a model of entire shop floor accurate enough to yield useful results is time consuming and resource demanding.  In the Toyota Production System (TPS), the philosophy is to eliminate as much variation so that planning is simplified using deterministic tools. This case study examines a facilities layout plan for a greenfield manufacturing plant that practices TPS. Here, a TPS focused Systematic Layout Planning tool is largely used for the deterministic portion of the planning while a digital (Tompkins, White et al. 2010) twin is used to specifically model a new automated material handling process with high uncertainty within the plan.  The results demonstrate the benefits of this deterministic approach coupled with a highly-focused digital twin portion for achieving optimal facilities layout in a timely manner.