We study the critical factors that govern the 2D-crystal quality of self-assembled nanoparticles using convective assembly (“blade-casting”) technique. The goal is to improve crystal quality by both maximizing monolayer coverage and optimizing crystal width. We find that crystal quality is enhanced by air plasma treatment of the substrate surface, while the monolayer domain size increases with assembly at higher substrate temperature. In addition, we correlate the meniscus shape to array thickness obtained at different deposition stages. Our results provide insights toward scalable production of well-ordered nanoparticle monolayers for applications including biosensors, optically-active surfaces, and nanocomposites.