If the fish still have heads, chop them off. Then pull out the backbone with your fingers. (This is easier to do than it sounds. Simply grab the top of the backbone and pull it out and down; most of the larger bones attached to the backbone will come out, too.) Rinse off the fish.
Put the cleaned and partially filleted fish in a shallow bowl or plate and sprinkle the salt and soy sauce over them.
Peel the ginger and chop it into tiny pieces, about the size of a match head. Sprinkle them over the fish.
Smash the garlic cloves with the side of your cleaver, then peel. Chop the garlic into the same size pieces as the ginger. Add them to the fish.
Stir well to make sure that all the ingredients are evenly distributed over the fish, then set the fish aside to marinate at room temperature for 30 minutes.
Just before you are ready to begin frying the fish, add the flour. Stir thoroughly to make sure that the flour is blended with the marinade, and that all the fish are coated with the thin batter that is produced.
Heat a regular flat frying pan over a high flame for 15 seconds, then fill it with about an inch of oil. The oil should be ready for cooking when a slight haze has formed over it.
Gently drop the smelt into the hot oil (you may have to cook the fish in several batches depending on the size of your pan and the amount of oil you use) and fry the fish until they are quite hard and have turned a dark, golden brown; this may take up to 10 minutes. Remove the cooked fish from the pan with chopsticks or a slotted spoon and drain them on paper towels.
Note. These fish can be eaten as soon as they are cooked or you can fry them in advance and serve them at room temperature.