Preparing the Blank
Using a piece of carbon copy paper, I taped the final pattern along one edge to the wood, then I transfer the pattern using a slightly dulled pencil:
I used beech - cherry is a good substitute for handle material, as is walnut (though neither are quite as strong as beech, they should still be plenty strong). You'll want to avoid soft woods, or woods that are very open grained such as oak, as the open graining is uncomfortable on the hands after a time using them. The best saws from before WWII used apple wood, and beech became the standard sometime between the 1930's and 1950's, probably because of cost. You'll notice that the apple wood handled saws are more comfortable in general - it's not because of the wood, its because the manufacturer was more worried about quality, and more time was spent shaping the handle for a more comfortable fit. With the advent of electrically powered saws, the fine shape of the earlier saws fell to the inevitable onslaught of mass production and economy as hand saws fell out of favor as the preferred tool for cutting wood.
It's then a trip to the bandsaw to cut out the blanks:
There are some fairly tight curves to cut out, so I used a 3/16" blade. If there isn't a bandsaw available, a frame or bow saw, or even a fret saw can do the job just as well.
It's pretty darn important that the blade slots be cut straight so the blade doesn't mount in the saw cockeyed, so using a marking gauge to make a guide for the saw cut is prudent here. Afterwards, I trace the line left by the gauge with a pencil to make it easier to see. You don't want to mark past where you are cutting because it will force you to remove that mark it leaves later.
To make the cut, I use one of my favorite back saws - an old 'Warranted Superior' I've owned for years. It's been with me since before the dozuki years (and now I've returned to the western style as my preferred method), and had suffered silently from extreme dullness until I finally decided to get a magnifying lamp that allowed me to see what I was sharpening. But I digress... as I am using a panel saw as the source for the blade, I needed something that wouldn't leave too large of a kerf (which might leave the blade too loose in the handle) when I cut it. A backsaw blade is slightly thinner than a panel saw, so with the set of the teeth (which on this saw is fairly minimal) it ends up just a hair narrower than the thickness of the intended blade. You want to use a saw that tracks straight - adjusting for an off tracking saw in such a long cut is seemingly next to impossible.
Here I am sawing the slot for one of the stair saws. So what's wrong with the above picture? Take a look at where the handle of the blank is. I cut much deeper, and I risk cutting into the handle. Watch out when cutting the other way that you don't bash into the handle with the end of the blade, either. For the stair saws, the depth of the completed cut was like 1-1/4" or so - the actual depth isn't all that important, but there's no need to make it too deep, as you wouldn't want to compromise the structure of the handle body any more than needed.