Greg,
First. make sure your tang is slightly tapered, and the thickest part is at the front of the handle.
For the front of the handle, cut a block of wood/ivory to match the butt or stripe. It only needs to be 1/4" or so thick. CAREFULLY, saw/file the tang slot to make it an exact fit for the tang. One trick I use is to file the slot with the back side a little larger. This makes getting the front side ( the place that shows) as snug as possible.
Once the tang is fitted to the front piece, and the handle is pre-shaped as you wish, the handle can be assembled. Don't assemble it until you are ready to permanently install the handle.
Installing the handle:
On blades with tangs with enough thickness to allow the epoxy to be slowly poured in through the front piece slot, you can assemble the front piece onto the handle in advance. I usually put a thin coating of epoxy on both the front piece and the handle then put them on the tang. I hold them firmly in contact with each other as the epoxy gels, and once the work pot is gelled, but still a bit spongy, I slide off the assembled handle. Now, you can finish the handle. Once the handle is finished, tape it up to keep epoxy and scratches off it in assembly. TIP - mark the top side of the handle, as a taped up wa or oval handle can easily be put on upside down in assembly ( don't ask me how I know this

).
After the epoxy fully cures, you can completely finish the handle before assembly. When ready to install, fill the handle with epoxy and place on the tang as normal.The cork trick given below works well for assembling finished handles, too.
On blades with a thinner tang, pouring epoxy down the slot is nearly impossible, so the assemble is done along with handle glue-up.
Tape up the blade as you would for normal handle work. The only difference will be sticking a large cork on the point first. Champagne corks work great. I cut a 1/4" deep "+" in the outside end of the cork, and align it with the blade. More on that soon, now to installing the handle.
Place the front piece on the tang and wrap several layers of tape around the tang to make it stop where you want the handle front to be.
Place the handle on the tang and assure that the two fit together perfectly. Make any sanding adjustments needed now.
Remove the handle and fill it with epoxy. I like to use slow setting 24 hour epoxy, but the one hour type will work. 5 minute epoxy is far too fast.
Insert the handle, wiping off the run-out once it seats on the front piece. Wipe it off well and then take several large and heavy rubber bands, placing them across the butt on that end, and in the groves on the cork on the point. Put the bands on both the X and Y axes. Adjust the band tension from side to side as needed to make the handle sit firmly and straight against the front piece. Check that the handle lines up with the blade straight, too. Wipe off the excess again, checking for any gap. Place the knife in a vertical position and let the epoxy cure. I clamp a large spring clamp on the blade, which makes a tripod with the tip and allows the blade to sit vertically, but can be picked up for wiping or inspection. As the glue pot starts to gel, remove the rubber bands and the tape "stop" on the front of the handle. Wipe the handle joint off with acetone to double check that all is still aligned. If it is good, let it cure fully. If you are neat, and have done this a few times, you can leave the tape and bands in place and remove the rubber bands and tang tape after the epoxy is cured.
All that is needed now is to sand the front piece flush with the handle, and then finish sand the handle.