n a large shallow dish combine the soy sauce, maple syrup, rice vinegar, brown sugar, water, sesame oil, chili sauce, ginger, garlic and the pepper flakes. Whisk until sugar is dissolved.
Add salmon steaks to the dish and turn it around to cover it all in the liquid. Cover the dish with plastic wrap and let marinate for at least an hour in the refrigerator.
Brush well with oil a grill pan or the outside grill.
Grill the salmon on both sides, until salmon is cooked through or to your liking, about 4 minutes per side. While grilling the salmon, brush it with the remaining glaze on each side.
Garnish with green onions and sesame seeds before serving.