In a large salad bowl, combine the mixed greens, cucumber slices, and halved cherry tomatoes.
Arrange the flaked salmon pieces evenly over the greens mixture.
Gently add the diced avocado, distributing it throughout the salad.
Sprinkle the drained capers over the salad.
Drizzle with olive oil and fresh lemon juice.
Season with salt and freshly ground black pepper to taste.
If using optional ingredients like fresh dill, red onion, toasted nuts, or lemon zest, add them now.
Gently toss all ingredients until just combined, being careful not to break up the salmon and avocado too much.
Serve immediately for optimal freshness, or chill for 15 minutes to allow flavors to develop.