Producing garum was relatively simple. A garum maker such as Aulus Umbricius Scaurus would have first placed a layer of fish entrails on a bed of dried, aromatic herbs such as coriander, fennel, celery, mint and oregano.
Then he would have covered the fish entrails under a layer of salt about two fingers high. The layer sequence — herbs, fish and salt — was repeated until the container was filled. The concoction was then left in the sun to macerate for a week or so, and the sauce was mixed daily for about 20 days.
The process produced a smelly liquid — a local delicacy to the Romans.