Garum is a traditional Roman fermented fish sauce or condiment. It was used often in now-ancient Roman cuisine, as a condiment or sauce on its own, an additive to sauces, or as a seasoning.
Intestines of fish
Whole small fish
Salt
Salt the fish and fish intestines in a barrel.
Place said barrel in a warm, bright, place, turning regularly for at least 48 hours.
48 hours
Place a basket, cloth-covered colander, or similar into the barrel, and let the liquids seep up into the container.