In this study, to minimize the difficulties encountered in the surface profile and shape of testing samples in slake durability index test, a new sample preparation method that is called Pasha Method is used. In order to apply this new sample preparation method, marl block samples were collected at Tuncbilek open pit mine located at the Kutahya region in Turkey. Samples were prepared as two different profiles or shapes. The rounded test samples whose sharp sides were hammered and ground with abrasives were chosen first. These first testing samples were prepared according to both the ASTM and ISRM standard. The second test samples were equal-sized spheres that were prepared according to the new method.