We have developed a new technique called the slope nucleation method (SNM) for the growth of high-quality 4-dimethylamino-methyl-4-stilbazolium-tosylate (DAST) crystals. This technique combines the spontaneous nucleation and subsequent growth of a single crystal into one process. The SNM features the ability to control the nucleation position and the growth orientation of DAST crystals. Many single crystals can be grown simultaneously in one process. X-ray diffraction (XRD) indicates that the SNM is effective for growing higher-quality DAST crystals as compared to conventional spontaneous nucleation and the top-seeded solution growth technique. DAST crystals with an XRD rocking curve as narrow as 20.2 arcsec full-width at half maximum (FWHM) were obtained.