Clean your fish, for both times I made these I used 4 mackerel, remove the head, tail, insides, and clean well on the inside along the backbone. Leave skin on and bones in.
I took each fish and cut into 3 pieces, place all in a bowl with a lid.
Prepare your brine with ¼ cup salt for 2 cups of water. I do this separate so I don't make more brine than what is needed. Make a batch and pour over the fish pieces, make more as needed to cover the fish.
Refrigerate for at least 3 hours, I normally refrigerate overnight.
Remove the fish from the brine and rinse, place fish pieces in a slow cooker, add the olive oil, water, pickle juice, bay leaves, and peppercorns.
Put the slow cooker on Low setting for 3-6 hours, depending on size of fish, 3 hours for small fish, like milkfish, and 6 hours for mackerel. Check the fish about an hour before the time, you are looking for soft fish and soft bones, if the bones are not soft, go another hour and check again, repeat until the bones are soft.
When done and the fish and bones are soft, allow to cool and store in the fridge in olive oil.
Serve as is with or on a lettuce salad with tomatoes and garlic, or as a sandwich with bread spread with mustard.