If using raw octopus, remove and discard the eyes and beak and clean thoroughly. Sprinkle all over with salt and knead well to tenderize. Rinse under cold running water. To make the poaching liquid, pour the fish stock or clam juice, water, and vinegar into a stockpot into which a medium strainer will fit. Add the black peppercorns and bay leaves and bring to a boil. Place the cleaned octopus in the strainer and dip in the boiling liquid for 30 seconds. Remove and let rest for about 2 minutes. Repeat this procedure twice. Transfer the blanched octopus to a tray and refrigerate until cold. Strain the poaching liquid and reserve 1/4 cup. When ready to use, cut the octopus into bitesized pieces. Drain the soaked chick peas and, in a large pot, combine them with the water and the bay leaf. Bring up to a boil, reduce the heat and simmer covered for about 2 1/2 hours, or until tender. Drain well and discard the bay leaf. (Or, if desired, use canned chick peas for this dish: rinse and drain them well before adding to the salad.) In a bowl, combine the octopus, reserved octopus cooking liquid, chickpeas, lemon juice, parsley, oregano, salt, black pepper, and olive oil. Toss together until all the ingredients are well coated. Mound the salad onto a platter and place leaves of red leaf lettuce upright all around the edges. If desired, sprinkle with crumbled feta and diced tomatoes. Serve immediately.