I've always avoided stacking forges and cement mixers personally cos it looks so bad imo.I'm all for having pretty assets in the game, but I don't think the forge needs to be portrayed with all those tools and such. Who only has a single forge in their base? It is going to look really busy to see a bunch of those forge accessories repeated for each forge. Plus the waste of space to require them to be 1x2.
I have been building my forging area like this picture for years now.
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A better looking forge model is greatly appreciated from me.