Preheat your oven to 425 F. Place 4 frozen salmon filets still in their plastic wrap in a large bowl under cold running water.
Cover a half sheet pan or broiler pan with aluminum foil and place the salmon fillets on the foil. You don't need to oil the foil because you want the skin to stick for easy clean up. If you like to eat the skin, then oil the foil.
Sprinkle each piece of salmon with salt and pepper.
Mix the together the dijon mustard and olive oil.
Spread about a teaspoon of the mustard/olive oil mixture on each piece of salmon.
Place the pan on the middle rack of your oven.
Cook the salmon for 10-15 minutes. Check for doneness after 10 minutes by inserting a knife into the center of the salmon and if it separates easily and is opaque, it's done. Alternately, you can insert an instant read thermometer and cook the salmon to 145 F.
Using a metal spatula, lift the salmon off the skin.