Creative problem-solving skills are essential for navigating complex, non-routine challenges, enabling individuals to create unique goals, execute innovative procedures and generate original outcomes. While the link between metacognitive skills and the creativity of outcomes was established only recently, further exploration is required to understand their interplay in complex problem-solving. This explanatory sequential mixed-methods study investigated the role of metacognition in solving two ill-defined problem-solving tasks: an experimental Product Improvement Task and an ecologically valid semestral essay. Seventeen undergraduates performed tasks and provided monitoring judgments. Based on the originality of outcomes and accuracy of judgments, three clusters of students were identified: "skilled and unaware" students underestimating high performance, "unskilled and unaware" overestimating low performance, and "unskilled but aware" accurately monitoring low performance. Subsequent in-depth interviews investigated the essay writing process of each cluster. Skilled students effectively utilized metacognitive knowledge, created a unique problem representation, and gathered and synthesized new information to develop essay drafts that were debugged and evaluated. Unskilled and unaware students exhibited deficits in strategy knowledge and had poor metacognitive skills. Unskilled but aware students exhibited low self-efficacy and motivation to perform. These findings emphasize the need for targeted metacognitive and motivational interventions for different clusters of students.