Hew off sides again starting by making a rectangle.
Then take the corners off.
Now some people like to take the head off and saw a slit down the centre for the wedge I just split it with a knife or chisel. All we need is a small split to start the wedge in, a gentle tap on the back of the knife taking care not to go too far so the knife hits the metal.
Now this bit is important and its more art than science. Have a look at the gaps between handle and head. How big this gap is will depend on how accurate you have been with the shaping but also on the interior profile of the head. This head is fairly straight through inside so the gap is fairly small some heads are quite hour glass waisted inside so the gap would be much more. Now we need a wedge made from a cleft not sawn piece of dry oak, other woods will work but oak is best if you have it, very dry is important so I keep a supply of dry cleft oak siting near the fireplace. Imagine the wedge going a little more than half way through the head, at that point on the wedge you want it to be thick enough to take up all the gap between head and handle and a bit more to allow for a healthy compression. The end of the wedge I shape to have about 1mm flat then chamfer from both sides at 45 degrees this makes a strong but sharp leading edge to go into your split head.
It should take up all the gap and make a tight fit.
Shame I don't do leatherwork really or I could do a tutorial on a nice sheath for it.