It's tech from the 80s. Look up the Nishika N8000 and Nimslo 3D.

Basically it's multiple lenses next to each other, each capturing a small slice on the 35mm film. Every lens has it's own shutter, which is triggered at exactly the same time.

This wasn't too involved and quite cheap to implement with analog tech in the 80s/90s, but if you want to do the same thing with digital there's quite a bit more to consider. Here's a cool video of someone building a digital stereo camera: https://www.youtube.com/watch?v=_aofxbH0elo

The hard part with digital boils down to: Cheap camera modules are hard to calibrate to the same parameters and sometimes impossible to set focus, so pictures look the same. And taking pictures takes quite a bit of processing power, so if you want to take 4 pictures at once it gets a bit tricky with just a cheap raspberry or similar.