Add 1 cup of fresh blueberries to a large pitcher and lightly mash them just enough to release juice and aroma while keeping some structure, then add the fresh lemon juice, honey, and fine sea salt and stir thoroughly until the honey is completely dissolved and the base tastes bright and clean.
Pour in ice-cold water to reach a total volume of about 3.2 liters, then add the whole blueberries and thinly sliced lemons and stir gently to distribute without breaking down the fruit.
Refrigerate for at least 1 hour for a light, clean flavor; for a more pronounced blueberry character, let infuse up to 4 hours, but no longer, as extended contact dulls both fruit and citrus and muddies clarity.
Serve well chilled straight from the pitcher, or over ice if preferred, keeping the fruit in the water for aroma and visual freshness.
