Rub half the rim of a Collins glass with lime and coat with kosher salt. Muddle 4 cucumber slices in a cocktail shaker. Add 2 ounces tequila, 1 ounce fresh lime juice, 3/4 ounce agave syrup (nectar), and 4 dashes of celery shrub and fill with ice cubes. Cover and shake until outside of shaker is frosty. Pour into prepared glass.
