Bring 4 cups of water to a rolling boil in a medium saucepan.

Remove the saucepan from the heat and add the dried hibiscus flowers (or tea bags). Stir gently.

Let the hibiscus steep for 5-10 minutes, or until the tea reaches your desired strength and color. The longer it steeps, the stronger the flavor and deeper the color.

Strain the hibiscus tea through a fine-mesh sieve into a heatproof pitcher or jar, discarding the flowers. While the tea is still warm, stir in the granulated sugar until it dissolves completely, if using.

Allow the tea to cool to room temperature, then refrigerate for at least 1 hour, or until thoroughly chilled. Serve over ice, garnished with orange slices and fresh mint, if desired.