Preheat oven to 450 degrees F (230 degrees C). Spray two large pieces of aluminum foil with cooking spray.
Place salmon fillet on top of one piece of foil. Sprinkle salmon with salt, pepper, garlic and chopped dill. Arrange lemon slices on top of fillet and place a sprig of dill on top of each lemon slice. Sprinkle fillet with chopped scallions.
Cover salmon with second piece of foil and pinch together foil to tightly seal. Place on a baking sheet or in a large baking dish.
Bake in preheated oven for 20 to 25 minutes, until salmon flakes easily.