Simplest way is create a Google Slides and export a PDF or images for slides ... then vibe code something that ties the left menu to slide switching on the right side.
If you "Inspect" on your browser, you can see that each slide on the page is a JPG so he's probably doing something similar.
If you "Inspect" on your browser, you can see that each slide on the page is a JPG so he's probably doing something similar.