One other thing I'd say is - I personally don't use jigs and stuff - it's very easy to eyeball things quite accurately.
I'm not sure if I've mentioned this before but, I spend a relative amount of time on hand sanding. When I finish the initial shaping (on a belt sander, but chisel or plane would be the same), the handle doesn't need to be particularly accurate. Most of the final shape comes from the coarser grit sanding sheets, laid on a hard flat surface (180 and 240 grit do most of the work). You can be really nice and accurate with removing material, evening up angles, building in taper, etc. at this point. And it doesn't take very long, cos you can apply quite a lot of pressure.
You could actually happily make a handle just using sandpaper if you sawed a rectangular block of a similar size to begin with. Below are some wooden stakes my wife got from the hardware shop for instance. You could knock up a nice one or two piece handle from these in about an hour with a saw and some sandpaper. Or maybe even an atoma plate. I've not tried using one before on wood, but no reason it wouldn't work I don't think.
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