Prepare brine solution by mixing 2 liters of water with 1/2 cup salt. Soak sardines for 30 minutes to clean and remove blood.
Drain fish and rinse thoroughly with clean water.
In a deep pot, layer carrots, garlic, bay leaves, peppercorns, olives, and chilies at the bottom. This prevents the fish from sticking and burning.
Add sardines carefully on top of the aromatics.
Pour in water and olive oil until fish are fully submerged. Add salt.
Bring to high heat and allow the mixture to boil.
Once boiling, reduce heat to very low and simmer slowly.
Cook for about 5 hours, checking occasionally.
Continue cooking up to 8 hours until fish bones become soft and edible.
Once done, let cool before transferring to sterilized jars for storage.