Use two tablespoons of the oil to grease a baking dish.
Peel and slice the potato thickly. Cut the lemon in half, then slice one half thinly (set the 2nd half aside for a moment.)
Arrange the potatoes on the bottom of the dish, sprinkle some salt and pepper over them, then make a layer with the lemon slices. Sprinkle the garlic and dried herbs over the lemon, pour a few tablespoons of water in. Put the chicken pieces in, squeeze over them the juice out of the 2nd half of the lemon, sprinkle remaining tablespoon of oil over, season with salt and pepper.
Bake for 30 minutes. Take out of oven, turn the chicken, baste everything with the juices, return to oven and lower temperature to 375F / 190 C / Gas Mark 5 and bake for another 20 minutes. Remove from oven, drain off the juices into a measuring cup or heatproof mug, return to oven for a final 10 minutes or until the potatoes have crisped a bit and the chicken is browned and cooked.
Remove from oven, zap the reserved sauce in measuring cup in a microwave for a minute or so to heat it up. Arrange chicken on a plate, discard the lemon slices, arrange the potatoes on the same plate as the chicken, and pour the sauce over it all, and serve.
For herbs, use thyme, rosemary or whatever you have on hand. For chicken pieces, use drumsticks or thighs.