A detailed study of the morphological evolution of 2-dimensional LaF₃ nanocrystals under the thermal treatment in air was performed. XRD, SEM, TEM and ¹⁹F MAS NMR techniques were used to characterize the aggregation process of nanocrystals. ¹⁹F NMR relaxometry and diffusometry were applied to investigate changes in the dynamics of the fluorine ions. Heating of nano-structured LaF₃ above 800 K led to crystallite growth accompanied by a deceleration of ionic motion, as seen from the NMR relaxation and diffusion data. The effect is dependent on the annealing temperature, and its enhancement above 1000 K causes the morphology and dynamics of the 2D nanocrystals to approach that of the bulk material. ¹⁹F MAS NMR confirms that the local structure of annealed 2D LaF₃ is identical to that of the bulk material.