Line a baking tray or roasting tin with baking parchment. Preheat the oven to 190 C / Gas 5.
Mix together the sea salt and egg whites. Mixture should be slightly moist.
Spoon about half of the sea salt mixture onto the parchment-lined tray to make a 3cm-deep bed for the salmon to lay on. Pack down slightly with your hands. Lay the salmon on top. Salt the inside of the fish with regular salt to taste. Cover the salmon with the remaining sea salt mixture, and pack down with your hands so that the mixture is firmly encasing the salmon. (It is okay if the salmon tail sticks out and isn't covered by salt!)
Place the salmon in the preheated oven and bake for 25 to 30 minutes, or until the salmon reaches an internal temperature of 52 degrees C.
Remove the salmon from the oven and let rest at room temperature for 10 minutes. Crack open the salt crust and peel away. Peel away the skin and fillet the salmon in portions. Remove the spine and bones in one go, then continue with the other side.