I'm sure somewhere on here it's been done to death, how to make a slide, you can even find a ton of you tube video's using everything from string and lighter fluid, a bowl of ice water etc etc, score once blah blah blah.
Here's the easy method, never made one before in my life till just now, here's what I did, literally, it took less than 10 min to make 2 I needed.
First, I put a tea kettle on the stove with water to boil, while waiting, I took 2 plastic cups with large enough diameters for the large 1L bottles of wine to fit into neck first, filled the first one with lots of ice topped with cold water, took a standard hand held glass cutter you can buy anywhere from H-depot to Walmart, scored the neck by laying the bottle on it's side and slowly pressed against the neck turning the bottle, pressed hard enough to hear and see the glass scratch, even went over the area a couple times(they say score once only...bull puckey) made a good circle score around the neck, there's my water boiling, poured it into the other cup, proceeded to dunk the neck into the hot water up to and past the score mark, alternating between the hot and cold leaving it in no more than 30 seconds each, started to think it wasn't going to work, after about the 4th to 5th switch, "POP', perfect slide, did it a second time, took a few more dunks, assuming because the hot water started to cool off.
easy peasy, simple no mess, no combustibles, no cleanup, just lightly sand the breaks on the slide to avoid any sharp edges, I used Gallo Moscatto, a fine vintage for slides lol, hmm, maybe a good Riesling next....
Tried them already on my new 2x canjo builds from yesterday...WOW, never played a slide before, hard to believe a single string canjo got me grinnin like an idiot from ear to ear LOL, ;-)
glad to be of some help, about ready to start my 4-5 string banjo build using a 12" tambourine drum base
When sanding the edges clean, I use a bucket of water with a few drops of dish soap and wet/dry sandpaper... I take no risks.
I've done this with beer bottles ( Corona brand ), as well as mexican coke bottles and IBC root beer bottles.. only thing is I score and remove the wiggly tip part first then cut to length.
I need to put some cloth in there with my finger to keep it on, I just have small hands I guess.
Also - I was aiming only for stubby slides ala Shane Speal.