I did one of those a couple years back, wasn't much to it. There was no wedge, just a necked down stub on top of the handle and a metal plate with a hole on the center that was forced over the stub. It helped keep the stub centered in the eye and acted like an anchor in the epoxy. If yours is like this, please read on.
The epoxy should be in two parts. Mix them together in equal amounts (you'll need a lot) and pack it into the eye with the plate on the stub and the handle forced tightly in the eye. Make sure it goes in from the right direction... I used a nail to work it down in real good and get out all the bubbles. It was a slow-set epoxy so you'll have a lot of time. If there are any gaps around the bottom of the eye, the epoxy will try to run out, so you'll need to seal that area up temporarily (something like clay should work). After that, I set it up vertical and let it cure a few days.
It worked pretty good for a while but eventually cracked (the epoxy, not the handle) after I buried the maul too deep into a big maple round and got it stuck fast. Pulled up a little too hard trying to rock it loose and I heard it crack. Didn't stay on much longer after that. The handle itself stood up just fine, it took a lot of abuse and split a lot of wood.