Patchy particles with uniform patches of specific shape and size have been predicted to have a rich potential in fabricating new structures; however, an effective method to control the patch shape and size is still missing. In the method presented here, a template is used to assist the fabrication of patchy particles with patches of uniform shape and controlled size by use of the glancing angle deposition method (GLAD). Uniform shadowing effects are caused by the wall of the grooves carved into the surface of a silicon wafer. The ratio of template dimension to particle diameter and the angle of incidence of the metal vapor rays determine the patch shape and size. Mathematical calculations are applied to predict the patch shape and size. Scanning electron microscopy is used to demonstrate the efficiency of the method. Scaling analysis shows that the template-assisted GLAD method leads to a 3100-fold increase in patchy particle fabrication volumes compared to the template-free GLAD method.