We recently came across a resource from the University of Minnesota about Accessibility and Slide Presentations. We like how it covers the bases in making accessible slide decks.
One important point is:
Don’t start with a blank slide and build from scratch. Instead, use built-in slide templates like Title slide, Title and body, and Main point.
And a good idea that was new to us:
For slides where you do not want a title to appear visually, add a title for screen readers in the same color as the background.