I've only seen flint used to make fires thus far.
I know obsidian is in the game, and maybe used to make macuahuitls? Not sure.
Seems like including flint-knapping would be along the lines of the technology we're using.
Shape arrows heads, spear heads, blades (not as strong as steel but sharper).
Would need flint, obsidian, or chert(not in game I don't think).
Tools would be an antler hammer for the initial shaping. An antler point tool for finer shaping and sharpening. A thick leather thigh guard.
Just as a reference:
Didn't know it was a thing; when I read the title I thought you wanted a skill to steal flint from people