In a large bowl, stir together 2/3 cup coarsely ground coffee beans and 22 ounces cold water. Cover and refrigerate for 12 hours or up to 24 hours for a stronger brew. Line a sieve with cheesecloth and set it over another large bowl. Strain the cold-brew coffee; do not stir the grounds. Pour 3 ounces of the concentrate into each of 2 large ice cube molds and freeze until solid. Pour the remaining concentrate into a jar and refrigerate for up to 1 week. Makes about 10 ounces concentrate and 2 large ice cubes.