Peel the grapefruit and use a sharp knife to release the segments from their membranes. Do this over a bowl to catch the juices. Measure out 2 tablespoons juice to use in the dressing.
Spread the torn lettuce on a large platter. Arrange the grapefruit sections and avocado slices over the lettuce.
To make the dressing: In a medium bowl, whisk together the grapefruit juice, honey, lime juice, 1 tablespoon of the olive oil, the salt and pepper.
Drizzle the salad with the dressing. Sprinkle with the herbs and flaky sea salt to taste and drizzle with the remaining 1 tablespoon olive oil. Serve immediately.