A broach is a tool used to carve out the channel for the tang. I think Riverside Machine Shop sells a pattern of them. Others have ground them down from small saber saw blades leaving just 2 or 3 teeth and reducing the over all width or just cutting it from thin narrow stock and heat treating it. You can use them to enlarge a single hole or two connect two that have been drilled close together.
Another way that way posted by, I believe, Dave Stephens, is to drill a hole in the block for the than just slightly greater in diameter than the width of the tang and filling it with epoxy putty. You then coat the tang with petroleum jelly as a release agent and stick that into the epoxy until the blade is where you want it. You then remove the blade and let the epoxy cure. Later, when you do your final assembly, you just use a regular epoxy to glue the tang back in. Of course you will want a guard or something over the end of the handle to hide the epoxied hole.
Things to remember with a stick tang. One is that they need not be supper long, 2 1/2" will put it under most of your hand. It can, however, go all the way through the handle and be secured with a nut or peened onto a peening plate or block on the butt of the handle. If you want to make it longer, you can but it's more work and it will require extended bits. Drill with standard bits first to get your holes started straight and then go to extended bits. Even with extended handles you shouldn't have to make you tang over 6" long unless you're making a through tang on a extra long handle like some of the long bladed seax's.
Round the shoulders of the blade where it is joined by the tang. The greater the radius the less of a stress riser but the harder the fit to any furniture but don't let it be square. Use a square and a filing jig to keep the shoulders of the blade even. Don't make the tang too thin or too narrow which will be defined by the size and the intended use of the blade. It's also a good idea to put at least one pin through the tang for safety.
Doug