Cut the lettuce into 1-inch-wide pieces and place it in a one-quart jar or divide between two pint jars.
Make the brine: Add the sugar, pepper flakes, star anise (if using), soy sauce, vinegar, and oil to a small bowl and whisk until the sugar is dissolved.
Pour the brine over the lettuce until covered, add the jar lids, and set the jars in the fridge, where the pickled lettuce will last for about 2 weeks.
