Place salmon fillets in a large glass baking dish dish. In a medium bowl, combine the vegetable oil, soy sauce, vinegar, green onions, brown sugar, garlic, ginger, red pepper flakes, sesame oil, salt and pepper.

Whisk to combine. Reserve 2/3 cup of the marinade and refrigerate. Pour remaining marinade over the fish. Cover and and refrigerate for 4 to 6 hours.

Preheat oven to 400 degrees. Line a large baking sheet with aluminum foil and spray with non-stick cooking spray. Arrange the salmon on the prepared pan. Bake for 10-15 minutes, or until salmon is done and flakes easily with a fork.

While salmon cooks, add reserved marinade to a small saucepan. Bring to a boil over medium-high heat and simmer until thickened slightly, about 5 minutes.

Remove salmon from oven and turn on broiler. Brush salmon with reserved marinade and place under broiler for an additional 2-3 minutes. Sprinkle with sliced green onions and sesame seeds for garnish, if desired.