Self-assembly of gold nanoparticles (NPs) directed by a water/alcohol interface, followed by annealing at 48 degrees C, leads to macroscopic, dried, freestanding monolayer films as large as several square centimeters (see figure). The approach is free of sacrificial templates and polymer glue layers and independent of the chemical nature of the metal NPs, which means it can easily be generalized to different metal NPs.