In a glass measuring cup or bowl, combine 3/4 cup blueberries and 1 cup water. Microwave on high 1 minute.
Pour this concoction into a blender and add the lemon juice, remaining 1/2 cup blueberries, the remaining 3 cups water and blend well. Pour blueberry lemonade into a container and add Stevia to taste. Refrigerate to chill thoroughly.
Fill glasses with ice, pour the blueberry lemonade. Garnish each glass with a lemon slice, a few more blueberries and serve.