01 - Bring 4 cups water to a boil in a medium saucepan. Remove from heat and stir in dried hibiscus flowers. Let steep covered for 10 minutes.
02 - Strain the tea into a large pitcher, discarding the hibiscus solids. While still warm, stir in granulated sugar until completely dissolved. Add honey or agave syrup if using.
03 - Add fresh lime juice and 3 cups cold water to the pitcher. Stir thoroughly to incorporate. Refrigerate for at least 1 hour to allow flavors to meld and beverage to chill completely.
04 - Fill serving glasses with ice cubes. Pour chilled hibiscus tea over ice. Garnish with fresh lime slices and mint leaves. Serve immediately.