How to freeze a fresh fish and fish fillet

This method was given to me by my fishmonger and since the result was formidable I never freeze my fish without this simple method.
Clean the fish fillets of the whole fish inside out in cold water.
Dry them with kitchen paper.
Coat both sides of the fillets with olive oil, making sure to spread the oil evenly.
​Wrap the fillets in cling film, then place them flat in the freezer.
When you want to defrost the fillets, place them in the sink or a large container with water at room temperature.