We successfully grew a uniform and high-transmittance La-doped BaSnO₃ (LBSO) thin film by reducing the LBSO particle size and improving film uniformity. We report an alternating magnetic stirring and ultrasonication process that can effectively reduce the size of particles in the colloid. A two-step spin coating process can improve thin film uniformity. A two-step spin coating process consists of two main steps: aggregation and gradual evolution. Aggregation is achieved by a single coating, which causes the colloidal to particles agglomerate into uneven clusters on the substrate. The gradual evolution step improves the quality of the films by filling the pinholes left by the initial coating.