To clean the anchovies, snap off the head in the direction of the belly and pull down to remove the innards. Butterfly the fish by running your thumb from the headless end of the belly splitting it down to the tail, leaving the tail intact. Carefully lift up the backbone from the headless end to the tail, holding on to the tail to keep it intact while removing the backbone completely. Rinse the fish thoroughly and blot dry with paper towel.

In a small bowl, whisk together the vinegar, salt, and flour until the salt dissolves. Arrange a layer of the fillets with the skin side down in a deep ceramic or glass dish and pour the vinegar mixture over the top to cover. Repeat this layering with the remaining fish and then pour the remaining vinegar mixture over the top to cover them completely. Cover the dish with plastic wrap and refrigerate for 24 hours.

Drain the anchovies. Lay a couple of layers of paper towel on your work surface and arrange the anchovy fillets over the top with the skin side down. Cover with another couple of layers of paper towels, then gently press down over the top to dry the fillets thoroughly.

Clean and dry the dish thoroughly. Rearrange the fish fillets in the dish with the skin side down. Pour the canola oil over the top to cover the fillets completely. Cover the dish with plastic wrap and refrigerate for about 2 hours or up to 1 week before serving.

To serve, drain the anchovies and arrange them on a serving platter or among the plates. Season with a drizzle of extra-virgin olive oil, a sprinkle of parsley, and hot red pepper flakes and serve accompanied by crusty slices of bread.