Combine the honey and water in a small saucepan and heat gently over low heat, stirring just until fully dissolved without boiling; remove from heat, add the lemon zest, cover, and let steep for about 10 minutes, then strain through a fine-mesh sieve and allow the syrup to cool completely.
Add the lemon pulp to a large pitcher and gently muddle it just enough to release juice and light texture without turning it into purée.
Add the blended watermelon to the pitcher, followed by the cooled lemon–honey syrup and the fine sea salt, and stir gently until evenly combined; pour in the ice-cold water and mix again until the lemonade is uniform, light, and fully integrated.
Refrigerate for 1–2 hours until fully cold and aligned, stirring once before serving as watermelon naturally settles.
Fill glasses with ice, pour over the watermelon lemonade, and garnish with lemon slices and thin watermelon slices.
