The development of low-cost and highly efficient electrocatalysts is crucial for the widespread adoption of clean energy technologies. Single-atom catalysts (SACs) have attracted extensive attention because of their exceptional catalytic performance and metal utilization. However, conventional methods for synthesizing SACs often have disadvantages such as an extremely low degree of metal loading and limited yield. Therefore, techniques for the scalable fabrication of SACs with high degrees of metal loading for use in practical applications are strongly needed. In this review, we first explore various design strategies for synthesizing stable SACs. Afterward, we highlight recent advances in improving the mass activity of SACs with high degrees of metal loading and introduce a universal strategy for synthesizing SACs on various supports. Furthermore, we provide a summary of facile strategies for the large-scale preparation of SACs for various electrocatalytic applications, including the oxygen reduction reaction, oxygen evolution reaction, hydrogen evolution reaction, and CO2 reduction reaction. Finally, we discuss the challenges and perspectives of the large-scale production of SACs for use in practical applications. This review offers valuable guidance for the design of high-loading SACs.