In a small bowl, whisk together the hoisin sauce, ginger, soy sauce, vegetable oil, half of the scallions, and the crushed red pepper. Reserve 2 tablespoons of the marinade and refrigerate until ready to use. Pour the remaining hoisin glaze/marinade over the salmon in the bag, seal the bag, pressing out as much air as possible. Refrigerate at least 30 minutes but no longer than 10 hours. Flip the bag 3-4 times while the salmon marinates to ensure even distribution.
½ cup hoisin sauce, 1 tbsp grated fresh ginger or 1½ tbsp ginger paste, 2 tbsp low-sodium soy sauce, 1 tbsp vegetable oil, 6 scallions or green onions, ¼ tsp crushed red pepper