Add blueberries, fresh lemon juice, sweetener, and water into a blender. Blend until the mixture becomes smooth and fully combined, releasing the vibrant color and flavor of the blueberries.

Gradually add ice cubes and continue blending until a thick, icy slush texture forms. The consistency should be smooth yet slightly coarse for that classic slush feel.

Taste the slush and adjust sweetness or lemon juice depending on your preference. If you enjoy a more tangy flavor, add an extra splash of lemon juice and blend briefly.

Pour into chilled glasses, garnish with lemon slices and fresh blueberries, and serve immediately while cold and refreshing.