Grind the coffee: Grind whole beans to a coarse consistency, like raw sugar or sea salt.
Combine: Add 1 cup of ground coffee to 4 cups of cold filtered water in a large jar. Stir gently until all grounds are saturated.
Steep: Cover and steep at room temperature for 12 hours, or refrigerate for up to 24 hours.
Filter twice: Strain through a fine-mesh sieve, then filter again through a paper coffee filter or cheesecloth.
Dilute and serve: Dilute 1 part concentrate with 1 part water or milk. Serve over ice.