Where to start with building my own distro

I wanna make a niche novelty linux dstro and release it for fun on github.. why? because im bored and i like customising things and messing with linux. the only issue is i dont actually know where to begin, surely i wouldn't have to simply make it form scratch, there must be a blank base OS that i could use as a model and just download and edit the things on it.

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I did a similar project for work one time but i used linux mint as the base and while i would do the same again here i was worried if i released it on github or something just for the fun of it that the linux mint crew might get a bit mad. any advice?