Tables are not very accessible in PowerPoint. Most screen readers do not announce headers, and you can to enter editing mode just to navigate it. In addition, there is very little semantic structure in a PowerPoint table. They are best left out of presentations all together.
Section 7.1: Making Tables
Go to the Insert Tab, and select the Table Button.
Create a title for your table, make sure it is visible on the slide.
Give your table real headers. Go to the Table Design Tab, and check Header Row.
When creating a table, follow these rules.
Only have one header row, one header column, or one of each.
Do not use nested tables, split cells, or merged cells.
Use text and backgrounds that give a good color contrast ratio of 4.5 : 1 or higher.
This table has very poor color contrast and would be hard for anyone to read.
This table has a good color contrast ratio. This table is very easy to read for most readers.
4. Provide Alt Text (and a long description if needed).