This chapter presents an innovative approach to STEM education in K-12 through the utilization of an open-source and open-design robot named FOSSBot. The robot is developed collaboratively by Harokopio University of Athens with the support of the Greek Free Open Source Software Society (EELLAK) and emerges as a versatile educational tool adaptable to diverse student groups and academic disciplines. The chapter sheds light on the unique features of FOSSBot, emphasizing its applicability in various educational contexts, from kindergarten to university level. With a wide range of sensors and actuators, it constitutes a low-cost but compelling alternative to commercial robots, introducing robotics as a powerful tool for enhancing AI literacy and incorporating AI concepts across academic disciplines. One of the key strengths of FOSSBot lies in its adaptability to diverse academic needs. The chapter explores how the robot has been adapted to teach programming, data visualization, and AI concepts and algorithms in a simple way using visual blocks and explains how it can engage students across various disciplines, providing a hands-on and interactive learning experience. It explains how the educational robot can be a transformative tool for STEM education in K-12, contributing to the broader conversation on fostering AI literacy and integrating AI concepts across academic disciplines.