Clean the bonitos well, cut them down to the tail. Remove the gills and wash them. Soak them in a low saline solution - put about 2 tbsp sea salt in 4 1/5 cups (1 L) of water and leave the fish in it for the blood to drain away.
Wash them well once again. Pour sea salt inside and out and arrange them in a suitable container. Put them in the fridge for 48 hours. Then, shake the salt off, sprinkle with vinegar and leave them hanging by the tails in a cool and ventilated area, while placing toothpicks to keep their bellies open. Keep them out of the sun! Let them hang for 48 hours.
Wrap each fish in paper and arrange in a suitable container. Sprinkle sea salt between the wrapped fish. Leave them in a cool and ventilated area. After 3-4 weeks, they're ready for consumption.