A method for practical area upscaling of nanopatterning for light-harvesting and photocatalytic applications is presented. Large area electron beam lithography is used to design patterns of simple-shape nanoparticles. After evaporation of gold, ion beam lithography is used to slice nanoparticles with grooves as narrow as 17 ± 3 nm in width for the required spectral performance and light field enhancement. It is demonstrated by systematic numerical simulations that cutting grooves into the Si and SiO2 substrates up to a 10 nm depth augments the volume where the light-field enhancement occurs. The dominant component of the field enhancement in the groove is |Ez|2, perpendicular to the substrate's surface. The application potential of 3D-tailored nanoparticles in light harvesting applications is discussed.