This paper describes the results of a simulation study that evaluated the performance of different separations of the plant layout problem solved by bounded rational decision-makers. Seven problem instances from the literature were studied. We simulated the solution of a problem by a bounded rational decision-maker as a random search over the solution space. The problem was separated by identifying “subsets” of adjacent locations. The subset assignment problem partitioned the departments into subsets corresponding to these subsets of locations. Then, the subset layout problem assigned the locations in the subset to the departments. We considered separations with 2, 3, and 4 subsets. We also considered separations that first aggregated the departments before assigning them to subsets of locations. The results showed that separating the problem can lead to better solutions than solving the problem all-at-once, but some separations lead to worse solutions. Maximizing the flow inside the subsets generated better solutions than maximizing the adjacency of the departments inside the subsets. When fewer subsets are used, minimizing the cost inside each subset generated better solutions than minimizing the total cost. These results show that the quality of the solutions created by a design process is influenced by the choice of subproblems that make up the design process.