Making char cloth is really much simpler than described above. Put some pure cotton cloth in an altoids or similar tin. No holes are needed, just make sure it is completely closed. Put the container in a fire for 10 minutes or so or until there is no longer smoke or flame around the tin, and let it cool a bit before opening. Whatever is inside should be completely black.

This would also work with a stove or oven or any sufficient heat souce(of course doing this indoors would be a bad idea unless you have a way to vent the smoke), and for that matter you can use foil or any container that will not burn. FYI this is the same way charcoal is made(using wood), and it would probably work with many natural fibers and materials. I've charred bundles of bark and used it instead of charcloth to catch a spark.

There is a quicker and easier way to make charcloth if you don't have a fire: Hang the piece of cloth on the end of a stick, light it on fire with a lighter, wave the stick around a bit to get most of the cloth on flames, then drop the burning cloth into a metal cup, flip the cup over on the ground and step on it for a minute or so to keep a tight seal with the ground. This method doesn't work quite as well, because its hard to get the whole cloth on fire without burning up some of it, so you normally either waste a little of the cloth or end up with parially uncharred cloth.