A revised version of another Electric Smelter I found on here. I made blueprints for an input and output, as well as a modular piece that can be put in-between. The smallest amount of furnaces you have to have with the design is 12, and you can add as many modules as you like. I am unsure at what point the design would fail to feed furnaces, though.
Input is in the center line, and there are two outputs
Original: https://factorioprints.com/view/-L-AAXq7ipqWxC_bSSs7