Take the fillets out of the fridge 15 mins before cooking, so they reach room temperature.
Using a large frying pan or a skillet, add olive oil and set on medium-high heat. Season the pan generously with salt and pepper (and chili flakes if using).
When the pan is hot enough, add the salmon fillets, skin facing down. You should hear the familiar sizzling noise. This means the temperature is high enough.
Cook them for 5mins from this side (skin down) without touching them.
Turn the fillets upside down. Season and cook for 3 ½ mins and turn on one of the sides.
Cook for 3mins before finally turning to cook the last side for another 3 mins.
After that, the fillets should be beautifully brown from all sides and have crispy skin.
Serve with a slice or wedge of lemon and a side dish of your choice