Recommended · for some experience
DIY Buck/Boost Converter (Flyback) || How to step up/down DC voltage efficiently
Why people recommend it
Recommended as a dependable explanation of how buck and boost converters change DC voltage, useful if you want to build one rather than buy a module.
Watch for: Cheap ready-made modules exist if you only need the function
In their words
If, instead, you wish to know HOW they do it, there are plenty simple tutorials (examples: written, video).
Anichang on electronics.stackexchange.com, Aug 2019. CC BY-SA.