I make the stacked handles on a mandrel. It makes things much easier, as well as a lot neater. It is the only way to get a good handle shape if there will be some sort of guard. If doing a puukko style, you can do it all on the blade tang, but using a mandrel is still easier as far as I am concerned. The mandrel is a piece of 1/4" threaded rod. I have 1" by 1" plates of metal with a 1/4" hole in them for each end. I drill a 5/16" hole in each square of leather. Wax the rod and the plates well with carnauba wax or dip in paraffin. You start with a nut and one of the metal end plates on the rod. Have everything in place before mixing any resin. Obviously, you need to wear rubber gloves to do the assembly.
I mix a pot of clear coat epoxy ( system three clear coat), and dredge each piece through it as I assemble the handle. When the stack is full, I put on the other plate and nut and run everything down tight. Wipe off all the excess with paper towels and set down to cure until the resin is fully set in the mix pot. With system three clear coat that is about one hour. When the resin in the pot is hardened ( it may feel sticky, but will be solid), take off the nuts and set the handle in a vise with the jaws open enough for the rod to go between. Smack the upper end of the rod to drive it out of the handle stack. Don't twist the stack or do anything to it, just drive the rod straight down to break any resin bonding. If the wax was applied well, it should move easily. Leave it flush with the upper plate,don't pull it all the way out. Set the block aside to cure for 24 hours.
After the full cure, you can drill and broach the block to fit your tang. Before mounting it permanently for the final shaping, it is best to grind the block into a rough shape of the final handle. This is a lot easier as a block than on a knife. After fitting the block to the knife tang, I usually make a tang shaped mandrel in mild steel that goes through the block and sticks out both ends about 6 inches to get a good grip while rough shaping.
After the handle has been epoxied on the knife tang and shaped and sanded to its final shape, soak the whole handle in Neatsfoot oil for a day. Remove knife and wipe off well and set aside to cure slowly over a few days to a few weeks (the time varies a lot). Wipe it off every so often to remove weep-out. When the oil has dried, sand again and buff hard by hand with a soft cotton cloth ( NOT a buffer). Let dry a day or two again, then give a coat or two of leather wax and conditioner ( I like Atom wax) and buff again. This gives a handle that can take the abuse of an expedition to the Amazon if needed. You can skip the Neatsfoot oil step and just apply a couple rubbings of Atom wax for a very durable finish, too.
