Bruise garlic and thyme in a mortar, using a pestle, then add lemon juice and olive oil. Place chicken in a single layer in a non-reactive container, pour over garlic mixture, season to taste with sea salt and freshly ground black pepper, turn to coat, cover with plastic wrap and stand for 1 hour.
Preheat oven to 200C. Scatter lemons over base of a roasting pan. Remove chicken pieces from marinade, place in a single layer over lemon, scatter with garlic cloves and roast for 15-20 minutes or until golden and cooked through.
For roast garlic aïoli, blend half the roast garlic (from the chicken pan) in a food processor with yolks, lemon juice and vinegar. Add oil in a thin, steady stream until thick and emulsified, season to taste and serve with roast chicken.