Preheat and Prepare: First, preheat your oven to 200°C (180°C fan). Take a large baking dish (a 9x13 inch one is ideal) and line it with a large piece of aluminium foil, big enough to fold over and seal the salmon completely. Lightly grease the foil with a little olive oil or butter to prevent sticking.

Prepare the Salmon: Pat the salmon fillet dry with a paper towel. This is an important step as it helps the seasonings adhere and allows the surface to brown slightly. Place the salmon in the centre of the foil-lined dish. Season it generously on all sides with the salt and pepper.

Mix the Garlic Butter Sauce: In a small bowl, combine the melted butter, minced garlic, fresh lemon juice, lemon zest, chopped parsley, and dried oregano. Stir everything together until it's well combined.

Pour Over the Sauce: Carefully pour the garlic butter mixture evenly over the top of the salmon fillet. Use the back of a spoon to spread it out, ensuring the garlic and herbs cover the entire surface.

Add Lemon Slices: Arrange the thin lemon slices in a single layer over the top of the salmon. This not only looks lovely but also infuses the fish with a gentle citrus essence as it bakes.

Create the Foil Parcel: Fold the sides of the aluminium foil up and over the salmon, crimping the edges together to create a sealed parcel. This traps the steam and moisture inside, which is the key to a tender result. What works best for me is to bring the two long sides together first and fold them down, then fold in the shorter sides.

Bake the Salmon: Place the baking dish in the preheated oven and bake for 12-15 minutes. The exact time will depend on the thickness of your fillet. The salmon is cooked when it's opaque and flakes easily with a fork. You can check by gently parting the thickest part of the fish with a knife. For precise cooking, you can refer to the FSA guidelines on cooking fish safely.

Optional Grilling Step: For a slightly browned top, carefully open the foil parcel (watch out for hot steam!) and switch your oven to the grill setting on medium-high. Place the dish back in the oven, about 15-20cm from the heat source, and grill for 2-3 minutes until the edges are just starting to turn golden brown and the sauce is bubbling. Keep a close eye on it to prevent it from burning.

Rest and Serve: Remove the dish from the oven. Let the salmon rest in the foil for about 5 minutes. This allows the juices to redistribute throughout the fillet. To serve, garnish with a little extra fresh parsley and spoon some of the delicious garlic butter sauce from the bottom of the dish over each portion.