It started off as four square pieces of EN45, at a guess they were about 60 mm square and 6 mm thick. They were heated up and hammered together (with a power hammer, although I'd guess a fly press could to the same job), with the scale scrubbed off and lots of borax poured on the joins every time to stop impurities & oxidisation of the joint. Once they were properly welded together, the shape was drawn out into a long cuboid and the central portion had the corners hit to turn it into an octagon and then a hexadecagon. The square sections at the end were then held in a leg vice and a clamp and it was twisted round and round and round (about 20 times I think).
After that, it was gradually shaped to form a knife shape (mostly with a hand hammer this time), then left to cool very slowly in some vermiculite overnight. Then it was ground to roughly the right shape (leaving the bevel a millimetre or two thick to stop distortion) & heat treated. There was then about 3 hours of hand sanding before it went into a bath of ferric chloride for 1/2 hour to bring out the pattern. That's the point when I brought it home.
At home, I ground the bevel (with a water cooled grinder), redrilled two of the holes in the handle (as I wasn't happy with the position) and dunked it in some very cheap and very strongly brewed instant coffee. That was a bit acidic and brought the colour back into the ground bevel.
Final job was fitting the handle, sharpening and oiling the handle.
Hope that all makes sense.