You will want to take into account effective instructional design when creating your OER. Use repetition, frameworks, meaningful names, hierarchies, and careful presentation of new elements to help students absorb information from your textbook or resource. Take a look at these five rules of textbook development by BCcampus.
Think about students with disabilities as you begin creating your OER. Students who use screen readers or other assistive technologies will benefit if you pay attention to hierarchy in your textbook, describe images with alt tags, caption your videos and include transcripts, and follow other best practices. BCcampus has created this helpful Open Education Accessibility Toolkit that you might consult as you get started.
Below are resources that help with accessibility standards for OER.