There's another way to cut glass without using heat from a torch and without risk of explotsion. I'm not sure if this is covered in the "Glassdrilling 101" link that I saw posted previously, although I seriously doubt it.
Nickle-chromium wire has a high resistance to current, and so when ample electrical current is passed through, it heats up enough to melt glass. All you really need is a decent gauge of nickle-chromium wire (22-23 ga.) and a 6V battery with at least 6 amps (lantern battery). If you want to use a thicker wire, add a battery (maybe two) and connect them in series. The higher the amps the hotter your wire (up to about 760 C, then you might have a problem with melting your Ni-Cr wire).
The current methods of glass production include adding soda/lime in order to lower the melting temperature of the silica(glass). Most glass (excluding pyrex, which as borate added to it to increase the melting temperature) melts at approximately 550 degrees C or 1000 F or slightly below that.
So, get five or six feet of 11 or 12 gauge coated copper electrical wire, about 3-4" of nickle-chromium wire, a 6V lantern battery, and you're set to cut some holes!
I'm going to describe a single battery setup using 22 ga Ni-Cr wire. Cut a two lengths of electrical wire about two and a half feet long and strip the ends on both of them back by about 1". Twist each of your lengths onto opposite ends of your Ni-Cr wire. Try to avoid twisting your Ni-Cr wire onto the coating on your electrical wire. When the Ni-Cr wire gets hot (550-575C), it melts the plastic and it smells nasty! With the wire being that hot, it melts fingers too...so no touchie when it's running. Bend your Ni-Cr wire into a "U" shape to the desired width of the hole you'd like to take out of the glass. Twist a hand-length section of your coated electrical wire together a small distance away from your shaped Ni-Cr wire in order to create a "wand".
When you hook both ends of your electrical wire up to your battery, the Ni-Cr wire should almost instantly become super hot, so don't let it touch anything. Once you've got your current flowing, take a "gouge" out of your glass with your Ni-Cr wire wand. With a proportionate amp-to-gauge ratio, your glass should be able to be worked like a warm spoon in hard icecream.
If I haven't described this well enough or you have any questions about it, please feel free to message me. I haven't got any messages yet, and I'm welcome to the experience!