You can get the same basic CS education and write your own OS, it was in my 4th year CS classes, we mostly just implemented Minix 1.0 but you could get as weird as you want.
Then you have to make enough libraries to start porting things to it, or write everything from scratch.
One of my favorite hacks like this is SectorLisp, which fits a Lisp (sort of) in a boot sector.
You can get the same basic CS education and write your own OS, it was in my 4th year CS classes, we mostly just implemented Minix 1.0 but you could get as weird as you want.
Then you have to make enough libraries to start porting things to it, or write everything from scratch.
One of my favorite hacks like this is SectorLisp, which fits a Lisp (sort of) in a boot sector.