Thanks for the replies, guys.
I'm not actually sure if I explained it right. I could, of course, do it with slabs of wood, or I could drill from both ends; but I'd like to find a way to do it all with one piece without leaving a hole in the butt end.
I know this has to be possible, because I've seen knives with long tangs that are done this way (and I own a knife like this). I'm sure it isn't terribly difficult, because knives have been made this way for a long time...
Here is an example of what I am trying to do:
http://watanabeblade.com/english/pro/magurokiriknife.jpg
Those knives with long tangs end up like this:
http://watanabeblade.com/english/pro/23.JPG
These sites (among many other sites) describe how the handles are made:
http://hocho.o-1.jp/tec7.html
http://www.japanese-knife.com/forging/
However, I can't find any place that explains how the holes are made to drive the handle into!
I will look around for a long drill bit, though, and see if that works... I was just wondering if there was a "normal" way of doing this that I was overlooking.
EDIT:
Aha!
I finally found a site that (sort of) explains the process.
http://www.ragweedforge.com/mount.html
Apparently you can actually burn a slot into the wood. I had assumed I needed to have a hole first...
An alternative is to burn the slot. This was often done in early times since long drills (or drills of any kind) were not always available to the maker. Today, it's easiest if you first drill a hole though the handle, then burn the hole into a slot. This is how the Helle factory did the Viking handles. You can use a piece of steel shaped like the tang, heated to a nice red. Press it in the hole until you are almost where you want the blade to sit, then clean out the char to the final fit. It may take a few passes. Unless you are using a blade that will be heat treated later, do not use the blade you are going to mount. The heat will ruin the temper of the blade. If you are doing a number of knives with the same blade, I suppose you could sacrifice one of the blades as a burning iron, but it seems a waste. It shouldn't take long to file or grind a piece of mild steel to the shape of the tang.
There is also a good tip for getting holes to match up from both ends:
If you are using a drill press, you can make a simple tool to greatly ease the work. Clamp a block of scrap wood to the table of the press. Drill a shallow hole in the wood and fit a stub of nail or drill rod in the hole, leaving a little sticking out. Lower the table, but keep the stub in line with the drill. Now when you are drilling the handle, drill a shallow (1/4" or so) reference hole in the other end of the handle first. Place this hole over the nail and you will be sure of your hole direction. This makes it much easier to drill converging holes to form a slot. It also is a great help when you are trying to drill through a handle from two ends and get the holes to line up properly. If you are making a handle with a blind hole you can still use this to keep the hole in line. Just leave the wood a bit long until you drill the main hole, then remove the surplus with the reference hole.
Hope that helps someone.
I want to make a traditional Japanese knife handle, which is only cut (burned, actually, as I found out) from one end.