In design-based education, students use scientific concepts to inform their artifact-making endeavors. On the other hand, artifactmaking activities are meant to deepen students' conceptual understanding. However, no strategy has been described that explicitly links conceptual development and artifact-making endeavors in computer science design projects in an authentic way. To fill this gap, in this 'work in progress' study, we developed an instructional model for fusion designing and conceptual learning in CS education. A key component of the model is the 'intermediate design products' which play a critical role in connecting designing and conceptual learning. The model served to develop exemplary lesson materials meant to enhance students' algorithmic thinking. The materials were implemented and evaluated in four classes. The results suggest the model provides opportunities to improve students' algorithmic thinking. Furthermore, intermediate products turn out to be promising inputs for (formative) assessment of conceptual development in design projects by capturing and revealing students' misconceptions about basic CS concepts.