Add the frozen blueberries, lemon juice, honey, and ice cubes to the blender.
Blend on high speed until the mixture is smooth and the ice is finely crushed, about 30-45 seconds. You should see a vibrant, icy purple slush with a slightly thick texture.
Stop the blender and check the consistency; if it’s too thick, add a splash of cold water and pulse again to loosen it slightly.
Once fully blended with a slushy, icy texture, pour the blueberry slushie into frosted glasses.
Serve immediately, garnished with a fresh blueberry or a lemon slice if desired, to keep the icy shimmer and refreshing chill.