Compact without excessive clipping - I make sure everything looks like it could physically work.

Preconfigured for iron, copy and reconfigure it for caterium and copper.

Tutorial showing how I built it here: https://youtu.be/Tgxknxp3-Go

Same as this blueprint, except built with Mk5 belts like I made in the video: https://satisfactory-calculator.com/en/blueprints/index/details/id/7199/name/Compact+Stackable+Octo+Smelter

This is easily stackable into 16 and 24 smelter blueprints.