Preheat the oven to 350°F (180°C) while you prepare the ingredients. Wash, peel, and slice the potatoes. If you’re slicing by hand, place the thinner slices under the fish and the thicker ones around the edges so they cook evenly. Arrange the potatoes in the bottom of a baking dish and drizzle with a little olive oil. Place the trout on top, cleaned, with the head and backbone removed, and opened flat. Season both sides of the trout with salt and pepper.

Now make the lemon and oregano sauce to cover the fish. Zest the lemon and set the zest aside on a small plate. Squeeze the lemon and pour the juice into a small bowl. Add 4 tablespoons olive oil (about 60 ml) and 2 teaspoons dried oregano. Mix well with a spoon.