For those with ADHD or just don't have the time to watch:

He bought a Samsung Flip with a broken inner screen, removed the screen and split the phone in half, and turned it into a modern take on a slide phone.

To do so, he 3D printed a custom mold to replace the bottom half of the phone, and then shoved a Blackberry keyboard into it. Designed a custom hinge so that instead of flipping the phone open, you slide the keyboard out from behind and it drops below the cover screen—which is now the main screen—because he used a 3rd party launcher to make it behave as such. That way the phone is fully functional without the inner screen.

The only thing he didn't do (nor did he attempt to), is figure out a way to move one or both of the cameras. Since the phone no longer flips open, the two main cameras are now both selfie cameras and there is no main camera(s).