If you haven't already, make our teriyaki sauce. This can be done up to 1 week in advance.
Place fillets in a large tupperware or in a large Ziploc bag. Reserve teriyaki sauce, then pour the rest on top of the fish. Seal, then marinate.
When ready, place an oven rack about 6-inches from the heat source, then preheat the broiler to high. Coat a baking sheet lined with parchment with cooking spray, then place the marinated salmon fillets skin side down, allowing excess marinade to drip off. Broil.
Brush the fillets with the remaining teriyaki sauce, then serve immediately with sesame seeds and thinly sliced scallions.