Peel the potatoes and slice them thinly. Mix with 1½ tablespoon oil and season with salt. Then distribute the potatoes evenly on a tray. Put in the hot oven and pre-cook for 8 minutes in the upper third of the oven at 220 °.
In the meantime, cut diagonally into each trout four times. Salt and pepper the trout, cut 2 slices from the lemon and quarter the lemon slices. Put 1 piece of lemon in each of the incisions.
Mix the potato slices briefly with a wooden spatula. Place the trout on top and drizzle with ½ tablespoon oil. Cook in the hot oven at 200 ° on the middle shelf for 10 minutes.
Pluck the parsley and thyme leaves from the stems and coarsely chop with the garlic. Finely chop the herbs and garlic in a lightning chopper and mix with 3 tablespoon oil. Season the herb oil with salt, pepper and 1-2 squirts of lemon juice. Drizzle the herbal oil over the trout and cook for another 10 minutes.