honestly if you want to play around, you can just get borosilicate glass
The way to seal these is by flame, but if you want it to be implant safe, a hydrogen + oxygen flame is used for this because hydrocarbon based flames infuse the glass with impurities. there are “browns gas” generators used for this which basically create and store small amounts of gas on demand for this purpose, and have a small jet nozzle you use to direct the basically invisible flame at the glass.
I purchased one of these to play around with, but since we don’t use flame sealing and I’m basically afraid of it exploding in my face, I’ve never powered it up.