In this paper, we present a case study of KBS engines built thanks to our knowledge-based system (KBS) development platform Lama. The Lama platform enables the software-level composition of KBS engines (hence PSMs) for a given task from reusable reasoning blocks. This paper emphasizes engine design activity and shows how our platform helps easily create new engines or modify existing ones. Indeed, designers need help to build the problem-solving method (PSM) of an engine, appropriately for an application domain. The current available tools neither integrate designers' knowledge at the right level, nor ooeer development, integration and testing facilities to implement KBS engines. Our experience tackles problems such as PSM and ontology design and (partial) reuse. This involves aspects such as the choice of an appropriate set of reasoning blocks to cover the needs of a problem-solving task, with the right level of granularity. As a first experimental field, we focus on program supervision...