Single-crystalline plates of 430 mm x 430 mm x 17 mm were prepared by directional solidification of NaI in a graphite mold. The setup was heated in a standard chamber furnace under nitrogen gas at atmospheric pressure. The entire mold bottom was cooled with air. At high freezing rates the plates were polycrystalline and interspersed with bubbles. Low rates yielded single-crystalline plates without bubbles, when the melt depth did not exceed 20 mm. Only three days were needed for a complete run of melting, crystallization and cooling down. The dopant was homogeneously distributed in the plate except for the last-to-freeze zones. Samples doped with 0.1 mol% TII yielded luminescent light and energy resolution under Co-57 irradiation equal to those of scintillators grown with standard methods by different suppliers. The method described paves the way to growing even larger crystal plates at very low costs.