In a medium bowl, whisk together the olive oil, soy sauce, balsamic vinegar, green onions, brown sugar, garlic, ginger, red pepper flakes, sesame oil and salt, until dissolved and well combined.
Place the fish fillets flesh side down in an 8x8-inch glass baking dish and pour the marinade over the top of the fish. Cover with plastic wrap and let the fish marinate in the refrigerator for 4 to 6 hours.
Outdoor Grill: Preheat the barbecue or gas grill to medium-high. Oil the grill rack and adjust the height to 5-inches above the coals or heat source.
Remove the salmon from the marinade and place skin side down on the grill. Cover with the lid, and grill the fillets 8-10 minutes or until fish just flakes with a fork.
Pan Sear: Alternately, heat 1 tablespoon olive oil in a large nonstick skillet over medium-high heat. Place the salmon fillets flesh side down in the skillet; cook about 3 1/2 minutes per side until browned and the fish flakes easily with a fork.
Meanwhile, heat the marinade in a saucepan, over medium heat until reduced by half and drizzle over fish.
Cook's Note: If you like more heat, add more crushed red pepper flakes.