I always drop this book when people talk about writing or hacking their own OS etc:
https://www.amazon.com/Developing-32-Bit-Operating-System-Cd...
Can probably find it on a shadow library. Getting something to boot on x86 is a little tricky, because IIRC the CPU comes up in real mode, so you have to create your own boot sector and bootloader before you can even execute your kernel.
That book + Linux inspired me to write my own OS in 1995. My goal was to have an OS that booted directly into a modern GUI and fitted (with basic tools) onto a single 1.4Mb floppy, which I did manage.