Wash peppers and clean them. Remove the seeds. Wash the rice and put it in a pot. Add the chopped onion, thyme, salt and pepper. Pour 2/5 cup (100 ml) oil and 2/3 cup (150 ml) water in. Stew for 10 minutes on the stove.
Then fill the peppers with this mixture, dip each of them in flour. Arrange them on a tray. Pour water in, nearly submerging the peppers, with 1 finger width to spare. Cover the tray with foil for baking. Bake in a moderate oven at 392°F (200 °C) for about 50 minutes.
Ten minutes before they're done baking, remove the foil to get a light crisp on top. Arrange 2 or 3 stuffed peppers in a bowl and gently pour the sauce produced from the baking over them.