This document is a guide that outlines the slip surface optimization procedure in GeoStudio, specifically using the SLOPE/W software. It begins by discussing traditional methods for defining slip surfaces and introduces the concept of optimization, which involves incrementally altering the slip surface to improve limit equilibrium results. The guide details the optimization process, which includes dividing the critical slip surface into segments and adjusting the endpoints to find the lowest factor of safety. It explains the iterative nature of this process and the use of the Monte Carlo method for point adjustments. The document also presents numerical simulations comparing optimized and non-optimized slip surfaces, highlighting the differences in shape and factor of safety. Additionally, it addresses potential pitfalls in the optimization process and provides guidelines for ensuring realistic results. The importance of using optimization carefully, particularly after establishing a probable solution, is emphasized throughout the guide.