Modular design has proven to bring numerous advantages in the design and development of new products, but its relationship with the end user has been limited in practical scope. Previous studies analyze its applicability for prosumer users, but it has not yet been tested as a design method. This work presents a first application in a design workshop carried out during the conceptualization phase of a real project. The objective was to design a multifunction portable cart that complies with the characteristics of modular design and is focused on prosumers. This conceptualization was developed by designers and prosumers with the purpose of designing modular products for the prosumer. To do this, the key terms and the design method were explained to the participants. Subsequently, two group exercises were carried out to devise new applications and propose limitations and solutions. The workshop concludes with the individual conceptualization of the product, giving rise to 22 design concepts that were evaluated by the participants. Due to the lack of consensus, a second evaluation was carried out by the three coordinators of the workshop. The highest rated concept was fully evolved and developed, including manufacturing. The results offer conclusions on how the participants applied the method, what were the most applied characteristics of modular design, what manufacturing tools were proposed for prosumers and how to approach the method to non-specialized users. Keywords: design method, prosumer, modular design, workshop, conceptualization