Wash the fish and open it in half, cutting it lengthwise without separating it into two. Remove spine column. Wash it well again and dry it with a cleaning towel.
Sprinkle generously with salt and oregano. Place the fish in the sun for at least 6 hours.
Remove from the sun and place the fish in a shady and airy place in order to drain all night. The fish must not be totally dried, it must be juicy.
Sprinkle on the fish some olive oil (1-2 tsp) and grill it for 3-4 minutes on the grill mode of your oven. If you are lucky enough and have an actuall grill then you need 1 minute and your fish is ready (the skin of the fish must be on the bottom).
Serve with chopped parsley and some oil and lemon sauce (or just drizzle with lemon juice and olive oil on top).