Getting a regulated 12V DC supply can be extremely simple with something like a LM7812. However, I am trying to get a regulated 12V output with a supply that can range from 10V to 18V. My thought is to regulate down to 9V and then back up using a step-up regulator. Is this the simplest solution available?
You could make a buck - boost converter with wires, inductors and an controller IC. And then make a PCB. That takes design effort and some skill as noise (especially ground loops) can be problematic. There is also the issue of low output voltage regulation. Some switching circuits will output literally twice the nominal output voltage at very low /zero loads. So if this is important to you, a more complex circuit is required.
Or you can buy this for £55:-
It's just one module and does exactly what you want. This is the data sheet. It doesn't require any additional components most of the time. My philosophy is to only build what you can't reasonably buy. And TRACOPOWER will be able to make much better volts that most hobbyists.
If you can tolerate a 10% minimum load, then you can use a variant of these that's ~£40. I've use both and they're excellent (and I don't work for TRACOPOWER before you ask). You can always add a minimum load with a power resistor /on indicator lamp, but that kinda detracts from the otherwise high conversion efficiency (87%).