This document outlines an in-service training for teachers from March 15-19, 2021 on localizing and indigenizing intervention materials for least mastered competencies. It defines localization as relating learning content to local information and materials, and indigenization as enhancing curriculum competencies in relation to the learners' socio-cultural context. Examples are given of how to localize and indigenize specific math and science competencies using local community references. Least mastered competencies are defined as those not mastered by over half the class, not taught, or too difficult for learners. Teachers are tasked with identifying the least mastered competencies from the second quarter.