@wombat457, the OP: Are you looking for these patterned basswood sheets in order to build multiple buildings, or just one or two? If it's the latter, even as a former HO scale modeler, I'd suggest just going ahead with laying up the clapboard siding one over the previous one by hand, the same way you might put a row of shingles on a roof. After all, the building was originally built that way in the first place, and if you can put a strip of wood over the next strip in a reasonably straight fashion, and are doing only a few buildings, or even just one, it would save you time and gobs of effort over trying to find milling and cutting tools. For a one-off structure, you won't want that, IMO.
Now...I'm THAT guy who often says "when you are trying to build something, think like a manufacturer." And I do that myself, but only if I'm trying to make multiple copies, or near copies of something over and over again. I tend to lose interest if I have to do multiple copies of even a short run of whatever it might be if I have to do them five at a time, etc. One? Two? OK. But five? My eyes start to glaze over and the quality of my work starts to suffer.
However, and if it's just a one-off. Heck, man! Just scratchbuild it, old school style, right down to the individual plank of siding. I've got just such an HO building I found about four feet from me, and it's so quirky and unusual you would never want more than one of them on even a large layout.
In fact, in the case of this particular strangish structure, I laid strips of cut paper...sheets, and not wood, to represent clapboard, because it scaled out more accurately than did even the thinnest basswood sheet's I could find. And that was in HO. In N-scale, paper is almost always the way to go, IMO.
Of course, it you want to build fifty and sell them as a kit builder, well...then you WOULD be a manufacturer...in which case machine cutting solutions are, indeed, what you want.