Biometric recognition systems have gained widespread adoption due to their effectiveness in providing secure and convenient authentication. However, unlike credit cards and passwords, which can be canceled and reissued when compromised, biometric data is permanently linked to the user. As a result, people are growing more worried that biometric technology may compromise their personal biometric information and, therefore, their privacy. For this reason, to prevent the leakage of biometric information, it is desirable to protect it through revocable and irreversible transformations to generate cancelable biometric templates. Feature transformation-based biometric template protection (FT-BTP) is a promising solution to address these challenges. It involves applying a mathematical transformation to the biometric template, which is typically non-invertible. Consequently, it becomes difficult or impossible to reconstruct the original biometric data from the transformed template. This chapter aims to thoroughly understand FT-BTP methods, offering a step-by-step guide for researchers, practitioners, and students interested in this field. This chapter is intended to be a self-contained tutorial, but the reader will be referred to recent reviews and papers for additional details. A set of study questions and links to some open-source implementations of FT-BTP methods are provided at the end of the chapter.