How to make cold brew at home, from "scratch"
So, you want to ignore the three well-meaning recommendations listed above, and do things the hard way. Cool! I bet you are the type of person that doesn't use Google Maps while driving because that wouldn't be "fun." At any rate, you're in luck -- you can make cold brew at home without the use of one of these fancy machines. In fact, all you need is a Mason jar. And if you are under the age of 35 and/or planning a wedding, chances are you've probably got more than a few of those.
Step 1: You're going to need beans that are as coarsely ground as possible. If the beans are too fine, there will be sludge and grime and all things unpleasant. The beans themselves are just a matter of preference -- but again, you'll probably want to grind them yourself to ensure they are as coarse as possible.
Step 2: Snag a large Mason jar (or really, any big, preferably glass container with a lid). You want about a 1:8 coffee-to-water ratio. Put your ground at the bottom of the container, and pour your water in. Cold water!
Step 3: Stir your concoction…. gently.
Step 4: Cover, then place inside your fridge for 12-24 hours. You don't have to put it in your fridge, but if you have one, you might as well.
Step 5: When it tastes like something you'd want to drink (not too strong, not too weak, Goldilocks stuff) strain it through a sieve, cheesecloth, or even a coffee filter to remove bigger clumps of grounds. Do this several times, till there's no dusty residue on the bottom of your brew.
Step 6: Serve! Add some milk. Drop in a dollop or two of sugar. Pour over ice. You just made cold brew, kid!