Add ground coffee and water to a large jar or resealable container (you can easily double or triple the recipe depending on how quickly you'll drink it.)
Set the container aside on the counter for about 12 hours - allow it to steep longer if you prefer stronger cold brew.
Once cold brew has reached desired strength/flavor, strain the ground coffee from the cold brew. I recommend using a combination of triple or quadruple layered cheesecloth with a fine mesh strainer. Discard or compost the grounds.
Store cold brew in the refrigerator for up to a week.
Since this recipe technically makes cold brew concentrate, when you're ready to serve, you can dilute with some water until it reaches the desired flavor and/or pour over plenty of ice. I usually just use a ton of ice and no water, but find what combo you like to reach the right strength and flavor.