Not sure if they are still around, but a few years ago there was a Chinese CRT electronics kit. They gave you a small monitor and you soldered all the electronics together to get it working. So might want to look for that.

https://www.youtube.com/watch?v=cRr6OTpLGD8

As for making the CRT itself that is on a whole other level with chemicals, vacuum pump, etc. Even if you could do all that you still need the electronics to drive it, so start there.