In a large bowl, combine 6 cups cold water and ¾ cup rock salt. Stir until salt is dissolved.
Add bangus and soak for about 30 minutes. Drain well, discarding liquid.
In a pressure cooker, layer bay leaves, carrots, and garlic to cover the bottom of the cooker.
Arrange fish in a single layer over the vegetable and spices.
Evenly distribute green olives, sliced sweet pickles, peppercorns, and chili peppers.
Season with 1 tablespoon rock salt.
Add olive oil over the fish.
Add enough water to fully cover the fish at about 1 inch.
Close and lock the lid of the pressure cooker. Cook over medium heat until the valve begins to whistle.
Lower heat and continue to cook for 1 hour and 10 minutes.
Turn off the heat and release the pressure by lifting the valve with tongs.
When the pressure fully dissipates, carefully open the pressure cooker lid and allow the sardines to cool.
Transfer into airtight containers or sterilized jars if using.