Business process modelling is a tool for requirements engineers or business analysts to express business requirements in terms of what activities are to take place when the application software executes. Since business process models can be shared by different organisations or business domains, we can apply the concept of software component fabrication to the fabrication of process components. A business process model will be partitioned into subprocesses, each of which is a process component that may be used as part of other business process models. This paper proposes an approach to designing process components by using a genetic algorithm. Based on a fitness function, the approach can give a recommendation for a process components design that optimally achieves managerial goals, i.e. cost effectiveness, ease of assembly, customisation, reusability, and maintainability. We present our approach via an example of a flight reservation system.