Whisk together the chickpea flour, salt, 2 teaspoons olive oil, and water, until no clumps remain. Allow the socca batter to rest and thicken for at least 30 minutes, and up to 2 hours. In the meantime, preheat your oven to 450F and place a 10 or 12-inch skillet into the oven.
Add one teaspoon oil to the skillet and swirl or brush it around to coat. Pour the socca batter into the hot skillet (it'll sizzle, so be careful!). Transfer the skillet to the oven and bake for 10-15 minutes, or until the socca has set and the top is golden. For a crispy top, you can bake for 10 minutes, raise the oven heat to a broil, and put the socca in the broiler for the last 2 minutes of cooking.
While the socca bakes, blend all green goddess dressing ingredients together till smooth.
When the socca is ready, brush the top with the remaining teaspoon oil. Top with the greens and avocado slices, then drizzle generously with the green goddess dressing. Serve.