I completed my Cross-Linux From Scratch distro in 2014, targeting the original Raspberry Pi since I was frustrated with the lack of (at the time) minimalist distros.

It was extra-hard, due to the cross-compiling nature of targeting the ARMv6 cpu family - but I learned a massive amount along the way.

Even though CentOS-minimal was released for Raspberry Pi by time I completed the project, I had so much fun it didn't matter. I ended up making a custom build system, consisting of a hodgepodge of bash scripts all wrapped together with a Makefile. My self-hosted Jenkins build server (old mini computer shoved on my book case) would run builds and produce the image artifact - those were the days...

The final distro image was ~40MB, which was impressive to me on it's own.