The most straightforward example to make you familiar with how to create a custom SPFx Yeoman generator is to use Yarn instead of NPM as your default package manager. The approach to change the default package manager is simple, and many people already use it as there default package managing solution.
So, instead of adding the ‘–skip-install’ option whenever you start a new project just add this option to a generator.
The first step is, as always, to create a new NPM package.