You can install Grackle Slides here.
When opened, it scans all the Slides in the Presentation for accessibility issues.
When the scan finishes, Grackle Slides arranges the document’s elements and structures into 5 categories.
- Sheets
- Tables
- Charts
- Content
These categories can be seen in the user interface on the right side of the screen.
Elements in each are marked as either accessible or inaccessible. Changes are made by selecting and editing these elements in these categories. For example, images should have alt-text.