Combine the gochujang, soy sauce, and maple syrup together in a small bowl. Arrange a rack in the oven about 8 inches under the broiler. Rub a baking sheet with a thin layer of cooking oil and place the salmon on the pan. Sprinkle fish with remaining ½ teaspoon of salt and broil for two minutes, then remove from the oven.
Drizzle or brush the glaze onto the salmon (you may have some left over) and return to the broiler. Cook for another 2 to 5 minutes, depending on the thickness of the filets, until salmon is cooked through and glaze is bubbly.
Remove fish from the oven and transfer to a serving dish. Sprinkle fish with sesame seeds and scallion greens. Use a slotted spoon to spoon the cucumbers alongside the fish. Serve with rice.