These can be opened by clicking on one of the panels, then you advance with arrow keys. Get out again with your Esc key.
You might get stuck if you interact with the full-screen video controls - you can refresh the page to start the slide over, and regain use of the arrow keys.
Please use the linked accessible versions for simpler down-the-page reading.
There are various versions, with various levels of jank and accessibility, my apologies in advance!