For tapenade, process olives, anchovies and garlic in a small food processor until finely chopped, then gradually add olive oil until smooth. Season to taste and set aside.
Heat 100ml olive oil in a saucepan over medium heat, add onion, garlic, coriander seeds and saffron, and stir occasionally until tender (3-4 minutes). Add carrots, vinegar and 25ml water, and simmer until carrots are just tender (4-5 minutes). Remove from heat, add coriander leaves and season to taste.
Preheat grill to high. Brush sardines lightly with remaining olive oil, season to taste, place skin-side up on a lightly oiled baking tray and grill until just cooked (1-2 minutes). Transfer to a serving plate, spoon on hot escabeche and cool to room temperature.
Toast bread under grill, turning once (1-2 minutes each side), rub with cut garlic and spread with tapenade, and serve with sardine escabeche scattered with micro-coriander.