Remove wide strips of zest from 2 lemons with a vegetable peeler (do not remove the pith). Make 2 cups simple syrup (recipe below), adding the lemon zest before heating. Let cool, then pour into an ice-filled pitcher. Stir in 1/2 teaspoon salt, 2 cups each fresh lemon juice and water, and some lemon slices.
Simple Syrup: To make 2 cups simple syrup, bring 1 1/2cups each sugar and water to a boil, stirring until dissolved. Let cool.