Cut the fins and tails off the sardines. Working from tail to head, scale with the blunt side of a small knife. Cut off the heads and remove the entrails. Rinse under cold running water. Dry carefully with paper towels. Heat 1/2 cup olive oil in a large frying pan over high heat until sizzling hot. Place the flour in a plastic bag with the sardines and toss until coated. Add the sardines and cook until lightly browned. Remove from the pan and drain on paper towels. Place the sardines in a nonreactive shallow gratin dish. In a medium saucepan heat the remaining olive oil over low heat. Cook the onion, garlic and carrot until softened, about 5 minutes. Add 1/2 cup water, the vinegar, chili, saffron, bay leaves, thyme, salt and pepper and bring to a boil. Reduce the heat and simmer for 15 minutes. Strain the sauce and pour the liquid over the sardines. Pick the bay leaves and carrot out of the strainer and sprinkle them over the sardines. Arrange the lemon slices over the sardines. Cover and refrigerate 24 hours.
