During the last decade, great attention has been devoted to supported metal single-atom catalysts (SACs), due to the maximal metal utilization and the unique reactivity of such materials. The preparation of high-loading, stable isolated metal atoms with the desired local environments remains the main challenge for the industrial application of SACs. In this chapter, we discuss in detail the most representative methods for the preparation of SACs on oxide and hydroxide supports to give to the reader a complete idea of the different steps of each procedure employed and the final stability of the deposited single atoms. Moreover, we focus our attention on the “bottom-up” methods, which represent a facile and universal route for the direct preparation of SACs on metal oxides and hydroxides.