A while ago I found an online archive of a slot car magazine (whose title I cannot remember, and which I can't seem to find again) which carried, in each issue, suggested layout plans. Particularly interesting were the ones representing real-world circuits and how they had been designed.
In short, the design process was to replicate the signature corners or combinations of a particular circuit, and then assemble them into a layout fitting within the specified space. Usually the result did not, at first glance, look anything like the 1:1 track, but, on careful examination, it would include all the major elements that make the real thing what it is.
It's certainly not the only approach to track design, but I found it very interesting.