Add lemon slices, chilies, garlic, mustard seeds, peppercorns and allspice berries. Stir in olive oil and mix well. Spoon mixture into a large jar with a tight-fitting lid. Screw on lid tightly and turn jar over several times to ensure ingredients are well mixed. Let olives marinate at least 1 week before serving, turning jar several times a day. Store up to 6 months in a cool place. NOTE: Use a mixture of corn oil and olive oil for a more economical marinade. Add sprigs of dried herbs to marinade, if desired. To serve, garnish with lemon twists and a fresh parsley sprig, if desired.