Prepare the Courgettes: Wash and dry the courgettes. Slice them lengthways into even 1cm-thick pieces.
Make the Marinade: In a mixing bowl, combine olive oil, lemon juice, salt, pepper, and chilli flakes. Stir well.
Marinate: Brush the courgettes with the marinade on both sides. Let sit for at least 10 minutes.
Preheat the Grill: Heat the grill to medium-high (400-450°F). Lightly oil the grates to prevent sticking.
Grill the Courgettes: Place the slices directly on the grill. Cook for 3-4 minutes per side until lightly charred and tender.
Finish & Serve: Remove from the grill and sprinkle with fresh herbs, toasted fennel seeds, and Parmesan shavings if using. Serve warm.