Buck, Boost..etc Is there always an IC for that?
It's always good to think about this kind of thing.  You can build a circuit like this without using an IC &mdash; and in fact if you look at the datasheets of the ICs in question they usually have at least a block diagram (if not a complete circuit diagram) that would give you a good start on replicating what they do &mdash; but in practice nobody uses such a design commercially because it would be more expensive than using the IC yet provide no practical benefit.  But for educational reasons, doing it yourself is a very good idea.  I haven't tried building a switching power supply using this kind of approach, but certainly simpler projects like op amps, logic gates and so on, building it myself from discrete components has often been very educational.