The self-assembly of 12 nm PbSe nanocrystals on a graphite surface during solvent evaporation is analyzed within the two-dimensional van der Waals phase condensation model. The interparticle attractive force, phase separation kinetics, and critical coverage in this system can be revealed from aggregation spatial patterns at different kinetic stages. Cracking in nanocrystal monolayer drying at high coverage reveals limitations of this model.