Engineers require scalable processes for patterning nanoscale features on sensitive substrates to enable widespread manufacturability of advanced nanoelectronics. Nanostencils have shown promise, but prior work has relied on electron-beam (e-beam) and focused ion beam (FIB) processes. Nanostencils also frequently exhibit significant edge roughness. Here, we present a fabrication process for nanostencils using double exposure optical lithography and a novel capillary-driven lamination technique to reduce edge blurring, demonstrating sub-diffraction limit features of ~200nm on poly(methyl methacrylate) films. We demonstrate the utility of these stencils by generating metal patterns for use with the 3ω thermal conductivity measurement technique. We find a thermal conductivity of 0.24 Wm-1K-1 and an anisotropy ratio of 9.7. This work demonstrates that nanostencils can be used for scalable, resist-free patterning of nanoscale features on sensitive substrates.