This paper describes the process of designing and prototyping a low-cost robotic platform based on existing equipment and projects that enable extracurricular STEM activities in Croatia and beyond. A robotic platform with a differential drive configuration was chosen for education from an early age due to its simplicity and a wide range of cheap and compatible components from which it can be made. From the aspect of integration into extracurricular or curricular activities, the BBC micro:bit ecosystem was considered, enabling block-based visual programming. Components with printable parts make up the assembly of the educational robot. The main steps in designing and creating a robot prototype are presented, which consist of the modelling, 3D printing of robot parts, and assembly into a functional system. After several stages of testing, an interactive workshop was held with 7th-grade primary school pupils. Further work is planned to create educational material for extracurricular STEM workshops.