Remove the salmon from its packaging and place the fillets on a cutting board. Pat both sides dry with paper towels to remove excess moisture.
Sprinkle sea salt evenly over the exposed surfaces of each fillet.
Preheat a large cast-iron or nonstick skillet over medium-high heat for 2–4 minutes, until the pan is hot (a small drop of water should sizzle on contact).
Carefully place the salmon fillets flesh side down (skin side up, if the fillets have skin) on the hot skillet. Gently set each fillet down rather than dropping it to minimize splatter.
Cook the fillets without moving them for about 6 minutes on the flesh side. Adjust this time shorter for thin fillets and longer for thick fillets.
Use a spatula to carefully flip each fillet and cook the other side for about 4 minutes, or until the salmon reaches an internal temperature of 145°F measured in the thickest part (or until it reaches your preferred doneness).
Transfer the cooked fillets to a plate and let them rest 2–3 minutes before serving to allow juices to redistribute.
Store any leftover salmon in an airtight container in the refrigerator for up to 4 days.