>Because you could also just pour molten metal into a mold and let it cool to get an initial "flat surface" but there are limits to that. I dont know what meta

>Because you could also just pour molten metal into a mold and let it cool to get an initial "flat surface" but there are limits to that. I dont know what metal would work for that. There's still significant surface tension in an open pour. I was casting some copper a few weeks back. A ~2CM piece had about ~3mm of surface curvature to it. Plus plenty of distortion from unequal cooling where it varied thickness as well.