Gather all ingredients: frozen blueberries, fresh lemons, honey (if using), and cold water.
Squeeze the lemons using a citrus juicer until you have about 1/4 cup of fresh lemon juice.
Add the frozen blueberries to your blender, along with the freshly squeezed lemon juice and honey if you prefer a touch of sweetness.
Pour in the cold water to help the blending process and achieve a smooth, slushie-like consistency.
Blend on high speed for about 30-45 seconds, stopping occasionally to scrape down the sides, until the mixture is silky and evenly blended.
Stop the blender and check the texture; it should be thick, icy, and smooth—like a frozen smoothie.
Pour the blueberry lemon slushie into glasses, garnishing with a fresh lemon wedge or a few blueberries if desired.
Serve immediately with a straw and enjoy this refreshingly icy treat.