To get the ATM Smithing Template, you need to brush suspicious clay at Ancient Cities.

To find an ancient city, you can use an Explorer's Compass.

It's a bit expensive but can save you a lot of time.
Once you find the ancient city, you will want to look for blocks like this:

The suspicious clay blocks will usually replace Polished Basalt. I would recommend flying around with night vision to find these blocks.
Once found, you can brush them and get the AllTheModium Smithing Template!

That is the easiest way to get the AllTheModium Smithing Template!