Self-assembly of nanocrystals into a macroscopic 3D superlattice has emerged as a promising nanostructure due to its collective optical and electrical properties. In this work, a macroscale supercrystal was constructed under constant temperature and humidity with an ultrasmooth Au nanosphere (NS) as a building block synthesized by a facile route. In particular, a reproducible and facile strategy was developed to fabricate highly spherical Au NSs with nanoscale size tenability. Importantly, this method does not require a syringe pump and breaks the limitation of instrumentation for the synthesis of Au NS, significantly contributing to the promotion and popularization of Au NSs. Meanwhile, an operable and cost-effective droplet slow evaporation self-assembly approach was applied to form a homogeneous 3D superlattice array against coffee rings with an enhancement factor as high as 1.37 × 10