Preheat oven to 450°.
Line a baking sheet with foil, making sure there's extra foil hanging off the sides and place the salmon skin side down on the foil.
Combine the salmon marinade ingredients (olive oil, garlic, thyme, parsley, salt, and pepper) in a small bowl and stir.
Brush marinade onto the salmon, making sure salmon is coated. Fold up the foil so that it covers the salmon; you want the salmon to be covered with the foil.
Place salmon in the oven and bake for 12-15 minutes or until salmon is cooked through. Then, turn broiler on and broil salmon for 2-3 minutes.
While salmon is cooking, make the salad: Heat olive oil in a large skillet and add bacon, leeks and thyme. Cook on medium-high heat for 5 minutes or so or until bacon is cooked.
Add watercress to the skillet and stir until everything is combined and watercress is cooked.
Transfer salad to plates and place salmon on top.