Prep the fish: Pat the fillets dry and place them on a heatproof plate that will fit in your steamer. Sprinkle lightly with sea salt.
Set up a steamer: Fill a wok or large skillet with 1-2 inches of water. Bring to a simmer.
Scatter ginger over the fish. Place the plate with fish into the steamer basket or directly in the wok/skillet (on a trivet above the water).
If you don’t have a steamer, you can bake the fish in a parchment packet (en papillote) at 375°F for ~12–15 minutes.
Steam gently for 8–10 minutes (depending on thickness) until the fish flakes easily.
Finish: Remove from the steamer. Drizzle with coconut aminos and a touch of sesame oil, then sprinkle with scallions.
Serve immediately with lemon or lime wedges.