Dump a pound of dark roast (coarse ground) into an appropriate container.
Add 4 cups of water. Wait 5 minutes for the water to soak into the coffee grounds.
Then add another 5 cups of water. Cover with a plate to slow evaporation. Let stand for 12-24 hours.
Use regular coffee filters to filter it into another jar.
Get a glass, fill it 1/3 with this coffee concentrate, top off with 2/3 water or milk.