There are three ways to do this:
1) Cut a slot the exact size of the tang in a solid block of handle material. It will be sloppy if not exact, and lining up rivet holes can be a problem. This seems like the best solution, but is not.
2) Make a two piece mortised handle. Take a pair of scales and mortise out one to make it have a recess slightly deeper than the tang. Glue up this side to the tang, drill the rivet holes through, sand the surface until it is flush with the tang. Glue on the other scale and drill it for the rivets. Install rivets and finish as normal. This is the simplest method, but leaves a slightly off center line on the handle. It works fine for a full hidden tang, too. With a carefully mated handle, the line disappears in the grain.
3) Make a three piece handle. Take a set of scales and a piece of thin material that is slightly thicker than the tang.The thin material can be matching or contrasting. Cut out the tang shape in the thin material. Glue the thin material to one scale and clean up any squeeze-out. Glue the tang to this assembly. Proceed from here as in the two piece handle. This method makes a nice centered two-line joint and looks really nice when done with a contrasting color to the scales. It works well with a tapered tang. The same method can be used to make a full hidden tang handle or a wooden sheath/saya.
Whatever method you use the same procedures apply about sanding and buffing the front of the handle before assembly. I especially like the three piece style of assembly with black Micarta and and red center spacers. I use Corby bolts and glue everything up at one time. You can use this style handle on kitchen blades for a good look.
Taking this method one step farther can make a stunning Japanese style handle for a sashimi or deba. Cut and fit a 3/4" long bolster block in black wood. Make the slot as perfect a fit as you can ( just like a guard). Since the only part that needs to be a snug fit is the outer end, I rout the slot slightly oversize ,from the back, all but the last 1/8", and then carefully file the last bit until it is a tight fit to the tang. Now, cut a thin piece (slightly thicker than the tang) of black wood in a "U" to fit the tang. Sand it until it is just about .050" thicker than the tang. Prepare two white scales for the sides. Glue and clamp up the white/black/white handle block. (Remember to pre-drill the single rivet hole in one side). Insert the tang and remove it while the glue is curing. Wipe it off, and re-insert it until it comes out clean. Let the handle dry. When assembled the white/black/white handle block should be a perfect fit for the tang. Sand the end flat to butt against the bolster block, checking that the rivet hole lines up, and glue the whole thing up on the tang. When sanded into a slightly forward tapering octagon, it is a really nice look- with the black bolster and the black stripe running down the center. I use holly wood, and have it stabilized. I have a few blocks of the same batch of holly dyed black and then stabilized. I cut these into 1" pieces for the bolster blocks, and 1/4" slices for the center strip.This gives me very stable ,matching grain, black and white wood. A single copper rivet or Corby bolt is perfect for this style, or go with a mosaic rivet.
I can't think of anything I'd use the router table for except this, otherwise it would be easier to make that purchase.
