1) Heat oven to 200C/180C fan/gas 6.
2) Rinse and dry the fish. Season all over, then stuff the cavities with the fennel slices, lemon, olives and basil.
3) Place the sea bass in a baking tray. If there are any stuffing ingredients left over scatter in the tray.
4) Drizzle with the oil and bake for about 30 mins or until cooked through and starting to brown.