Liquid glass is poured over a bath of liquid tin where it floats on top, gradually cooling until it can be lifted off, annealed to prevent cracking, cut and packaged.
Also, this all has to be done without oxygen, because tin dioxide will stick to glass
I’m so thankful for Wikipedia.
After years and years of using it for free and never contributing. I finally pulled the trigger 3 years ago and now I make recurring donations (~$25/yr). Absolutely no regrets.