2 fluid ounces gin
3/4 fluid ounce orange-flavored liqueur (such as Cointreau®)
1/2 fluid ounce fresh lime juice
2 dashes aromatic bitters (such as Angostura®)
Fill a cocktail shaker with ice; add gin, Cointreau(R), and lime juice. Shake in bitters. Shake well and strain into a chilled glass. Garnish with a slice of lime.