Place salmon piece(s) in a Ziploc bag or bowl/dish with sides. Pour half of the marinade mixture over the salmon, reserving the other half to thicken on the stovetop for a serving sauce. 

Marinate the salmon, turning occasionally, for at least 30 minutes or up to 3 hours. Preheat the oven to 450°F, and line a sheet pan or baking dish with aluminum foil and spray with non-stick cooking spray. 

Remove salmon from marinade, and place on the prepared sheet pan or baking dish. Discard the marinade in the Ziploc bag.

Bake for 15 minutes, until the fish registers 145°F in the center. Remove from the oven, cover with a piece of aluminum foil and allow to sit for 5 minutes longer. 

Transfer the reserved marinade to a small saucepan and heat over medium heat.

Make a slurry by stirring the cornstarch into the water until it dissolves.

While whisking, pour the cornstarch slurry into the simmering sauce on the stovetop and cook 1-2 minutes at a low boil until the sauce has thickened.

Place the salmon on a serving platter. Garnish with the prepared teriyaki sauce, toasted sesame seeds, and a sprinkle of sliced green onions.