In a large glass container, combine coffee grounds with 7 cups of water. Stir gently for a few seconds just to combine the coffee grounds with water (sometimes the grounds float, etc).
Cover the container with cheesecloth and leave it at room temperature for 12-24 hours. The longer the coffee steeps, the stronger the cold brew will be. It goes without saying, I maximize the stteep-time.
Line a large fine-mesh sieve with a few layers of cheesecloth, then place over another glass container. Slowly pour the cold brew over the cheesecloth to strain out the grounds. You can probably stop here, or you can punish yourself and filter the coffee again through something even "finer" like a sieve lined with a paper coffee filter.
(The punishment isn't that you're filtering it a second time; it's that the paper filter takes forever. But hey, you waited this long to make cold brew so what's the rush anyway?)
Discard the cheesecloth, any filters, and grounds (though I am now going to be exfoliating my face with used coffee grounds).
To serve cold brew, dilute it with additional cold filtered water to desired strength. Serve over ice with simple syrup, milk or cream. I used none of the above because I'm a fucking full-strength boss.
Cold brew will keep in your fridge, covered, for up to a week.