Splitting screen into 4 independent full screens

This is what I’m trying to do: run 4 Libre Office Impress slideshows in full screen mode on one monitor.

This is all running on a RPi4 8GB. (KDE runs very nicely on that if you haven’t tried it.) But I don’t have to run KDE and I don’t have to use Impress for the slideshow, lots of flexibility there. This is one of those things that “seems like it should be easy” but apparently it isn’t. Any advice would be appreciated, thanks a bunch.

Record screen videos of each fullscreen presentation.
Then install and log in to a tiling WM without window decorations like i3 or sway.
(Or you can find a way to remove window decorations in KWin.)
Open all four videos with mpv or mplayer (any player without decorations) so that they use a quarter of the screen each.