In a medium saucepan, combine sliced fresh strawberries, granulated sugar, and 2 cups of water. Cook over medium heat for about 30 minutes, stirring occasionally until syrupy. Strain through a fine mesh to separate solids and let cool.

Bring 2 cups of water to a boil, remove from heat, and add black tea bags. Steep for 5 minutes, then discard tea bags and stir in additional sugar if needed.

In a large pitcher, combine cooled strawberry syrup with the brewed tea. Add 4 cups of cold water and lemon juice, stirring well.

Fill glasses with ice cubes, pour the strawberry iced tea mixture over the ice, and optionally garnish with mint leaves or sliced strawberries.