Put the salmon skin-side down on a large baking sheet. Mix the olive oil, garlic and the lemon juice with a good pinch of salt and a few grinds of black pepper in a small bowl, then brush the mixture all over the flesh of the salmon. Add the sliced lemon on top and chill for at 20 mins.
Heat the oven to 200°C.
Grill the salmon, uncovered, for 10-12 mins, until cooked through.