Zest one orange with a microplane and place into a small jar.
Prepare oranges by cutting a small piece off the top and bottom, placing flat side down on cutting board, cutting away all peel and white pith, and slicing into thin rounds.
Place vinaigrette ingredients into small jar, seal tightly with lid, and shake thoroughly to emulsify.
Layer half of fennel and orange slices on a large platter. Drizzle generously with dressing and season with salt and pepper.
Layer remaining fennel and orange, along with avocado and walnuts, olives, or feta, if using. Drizzle with more dressing, season with additional salt and pepper, and garnish generously with fennel fronds.
Serve immediately and enjoy!