How to DIY a TEC temperature controller?

Hi, thanks so much for all the info here. I'm trying to do a DIY cooler, would anyone know what type of temperature controller can be used for these FX boards and how would it work? I tried looking around but only saw a circuit schematic but I honestly don't know how to read it. It seems like it's a variable resistance that sets low to high cooling from some of the videos but no one states where I can find those temp controllers and where to wire it to. Thanks in advance for any help here!

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