Method 1 - Ready to drink

40g coffee, coarsely ground
600g cold water Mixing ratio: 1:15

Method 2 - Concentrate

100g coffee, coarsely ground
600g cold water Mixing ratio: 1:6

I'm not a coffee nerd and take a relaxed approach to brewing. I actually use normal filter coffee. You can hold that like the roofers. Many sites recommend rather mild coffee and coarse ground. Just take your favorite coffee. But the quantities are independent of that.

I put the coffee in tea filter bags to save work and mess. I seal the tea bags with clips, put them in a large screw-top jar and fill with water.

Then I let the coffee steep at room temperature overnight (why always overnight?) for 12 hours. Sure - the longer the coffee brews, the more intense it becomes. But please do not let it steep longer than 24 hours.

After that, I remove the coffee bags and chill the coffee.

Method 1 - Ready to drink Fits if you do not want to extend the coffee further, so just drink with some ice or spices, as just "normal" hot brewed coffee too.

Method 2 - Concentrate

Fits if you extend the coffee with a lot of milk, syrup, ice or whatever.