Place the Nocellara olives in a fine-mesh sieve and rinse briefly under cool running water to remove excess brine. Drain well and pat dry with paper towels. Transfer to a medium bowl.

If you prefer to reduce brininess further, soak the olives in fresh water for 30 minutes, changing the water once, then drain and pat dry before proceeding.

Marinade

Prepare citrus and aromatics

Using a microplane or fine grater, zest the lemon (and orange, if using) into a small bowl. Halve the zested lemon and squeeze 1 tablespoon of juice into the bowl. Thinly slice the garlic cloves.

Warm the oil and bloom spices

In a small saucepan over low heat, warm the olive oil just until it becomes fragrant but not smoking (about 2 minutes). Add the fennel seeds and whole peppercorns and warm for 30 seconds to bloom their oils, then remove from heat.

Combine marinade

Pour the warmed oil and spices over the drained olives. Add the lemon zest and juice, orange zest (if using), sliced garlic, rosemary and thyme sprigs, and chili flakes. Stir gently to coat the olives evenly. Taste one olive and add up to 1/4 teaspoon coarse sea salt only if the olives are not sufficiently seasoned from their brine.

Marinate

Transfer olives and marinade to a clean jar or airtight container, pressing herbs and aromatics down so they are submerged in oil. Let cool to room temperature, then seal and refrigerate. Marinate for at least 12 hours, preferably 24–48 hours, to allow flavors to meld. Olive oil may solidify slightly in the fridge; bring to room temperature 30 minutes before serving.

Serve

Serve the marinated Nocellara olives at room temperature in a small bowl with some of the marinade spooned over. Provide toothpicks or small forks. Store refrigerated up to 2 weeks; discard if any off smells or visible spoilage appear.