It should be noted that I have a drip coffee maker and a diffuser, but I still prefer this method because it's so easy. And it uses no electricity. It creates very little mess. There's no heat or steam warming up my kitchen either.
Simply take an old jar with a lid and add your coffee to it as you prefer. I usually use about four teaspoons for this size jelly jar. Then fill the jar all the way to the top with regular water from your tap or filter. Put the lid on securely, then give your mix a few shakes. Put the jar in the back of the fridge and ignore for two or more days. I usually leave it in for three or four.
Then when you are ready to drink, grab a cheap coffee filter, filter basket, or heck even a piece of good cheesecloth will probably work. Place your filter into a food-grade funnel, place the drain of the funnel into a carafe or your cup. Shake the mix again, then pour into your filter/funnel contraption. The idea is to get all the grounds and coffee out of your jar and into your filter, then your cup. Take your filter and grounds outside and feed the plants with it.
I would be cautious not to leave your coffee mix for too long in the refrigerator. Any chlorine in your municipal tapwater should inhibit some bacterial growth, in theory anyway. Coffee has natural oils and compounds which can and do go bad over time, and I'm sure it would be a displeasing ferment. I don't let ours sit back there more than a week, not that it would ever last that long around here.