This study investigates the effect of nailing inclination angles on the stability of gypsum sand soil slopes, using 2D-Slope/W software within Geostudio 2018. The analysis focuses on gypsum sand soil with a 29% gypsum content, employing nine nailing inclination angles (5°, 10°, 15°, 20°, 25°, 30°, 35°, 40°, and 45°) across four levels of nailing. The nails are installed with a horizontal spacing of 2 m. Five slope angles (β) of 45°, 55°, 65°, 75°, and 85° were examined to evaluate their improvement under various nailing configurations. The study also analyses the effect of nailing length, applying the Mohr–Coulomb failure criterion to assess slope stability.  The findings indicate that the factor of safety (FS) consistently increases with larger nailing inclination angles, particularly as the angle rises from 5° to 40°. Similarly, an increase in nailing length enhances the FS across all inclination angles and slope geometries. Based on these results, nine design tables were developed, providing empirical equations to determine optimal nailing lengths, inclination angles, and slope conditions for effective stabilisation. These findings offer valuable insights for improving slope stability in gypsum sand soils and contribute to the optimisation of soil nailing techniques in geotechnical engineering.