Cook corn on the cob until tender and let cool. Cut corn kernels from cobs.
Place corn, tomatoes, cucumber, onion, and cilantro in a salad bowl. Toss to mix well. Add avocado chunks and toss gently.
Mix oil, lime zest, and fresh juice in a small bowl. Season with salt and pepper. Add chili flakes to taste, if you like. Pour over salad and toss one more time. Garnish before serving.