Here's a quick tip on the metalworks design that works best for me so far. It allows 4 smelters, kilns, and forges in a compact yet easily pathable space that also has room for expansion and decor. The initial design is an 'H' shape. This allows for modules to be placed on the inside, and maximizes available space. I then add smelters on one side, kilns on the other, and forges in the middle. The bridge of the H should be at least 4 spaces long. That way you can fit more modules on the inside. You may or may not need 4 charcoal smelters if you are also working a coal mine. For work orders, I have charcoal, iron ingots/pipes/plates, and copper ingots/pipes/plates set to minimum 6, and then forget about it for the rest of the game.