Thermal effects present a major challenge to scaling of solid-state laser to high-average power. When using a thin laser crystal disc with a nearly flat top pump profile, the heat flux can be considered to be one-dimensional. This results in a homogeneous temperature and stress profile within the laser medium leading to dramatically reduce the thermal effects. Some factors that may affect the homogeneous temperature profile are analyzed, such as the cooling dimension and the ratio of the pump area to the thickness of the disc. More than 120 W of an average output power is obtained with a 336 W average pump power by using a good design.