Writing your own textbook or other OER material is a time-consuming task. Here are some links that will provide some assistance.
OER Commons Open Author Open Author provides a place where educators can build and share high-quality open educational resources (OER), such as courses, units, lessons, activities and presentations, to meet teaching and learning needs around the globe.
This guide includes a checklist for getting started, publishing program case studies, textbook organization and elements, writing resources and an overview of useful tools. Authoring Open Textbooks by Open Textbook Network is licensed under a Creative Commons Attribution 4.0 International License, except where otherwise noted. See https://creativecommons.org/licenses/by/4.0/