Having never made a wa handle before, I set out to learn as much as I could. I found some excellent videos on YouTube. Wa handles are typically octagon (sometimes hexagon) or round. A ferrule is attached to a handle and then the whole thing would be drilled or burned to accept the tang of the knife. Rarely I see pins, but they do appear occasionally.
The traditional wa handle would have a ferrule of horn. As my horn supply is low, I am opting for ebony instead. Looking through my blocks I decided the colour contrast of ebony and maple burl would make for a warm handle. For a separating layer I have some 0.065" brass stock.
I cut about 1-1/4" off of a block of ebony and trim to an approximate cube with the band saw. I cut 3-3/4" of maple burl and a 1-1/4 square piece of 1/16" brass..
Permatex 84107. There are a lot of high strength epoxies, Gorilla, Acraglas, West Systems etc. will work fine.
Another approach preferred by some is to not drill the ferrule all the way through. This would hide the dowel and present a very clean ferrule front. If you do it this way, you'll want to make sure that your dowel is a little shorter and when compressing you can squeeze everything tightly together and not bottom out the dowel. Leave about 1/8" extra room for epoxy and you'll be fine.
Click here for Part 2 of the wa handle build.