Having been a kid living in a place that had open fires burning (new houses were under construction and the builders often made fires to get rid of scrap materials), I can say that the desire in the primitive mind to throw random things into a roaring fire to see what happens, is strong.
if some people chucked random ores into ceramic kilns, maybe one would get out some iron slag and then iterate from there
theres a great blog series about making iron.
https://acoup.blog/2020/09/18/collections-iron-how-did-they-...
its easy on paper, but when you get into the details its actually tricky