Slake Durability Index test is being widely used to determine the disintegration characteristics of the weak rocks when they are subjected to drying and wetting cycles. In the test standards, samples are recommended to have rounded or close to spherical shape. In this study, a new method called as Pasha Method was proposed and applied to prepare equal-sized spherical samples. Slake Durability Index tests were performed on the spherical and rounded sample sets prepared from different rock types. According to Slake Durability Index test results in all rocks, the difference between the first cycle and second cycle results of the rounded samples and the spherical samples is found as 0.05-8.04% and 0.1-13.63%, respectively. When only the spherical test results were considered, the difference in the first cycle and second cycle values is found to be 0.28-2.19% and 0.44-7.57%, respectively. Applying this new method allows researchers to perform this test on equal-sized spherical samples, resulting in the minimization of the shape effect on the test results.