Meanwhile, peel the remaining oranges. Use a knife to get all the pith (white membrane) off.
Cut one of the oranges in half and squeeze the juice into a small saucepan together with the measured water and the spices. Bring it to a low simmer and then remove from the heat and leave to steep and cool for 15 minutes.
Cut the oranges in 1/4-inch thin slices and arrange on a large plate.
Pour the spiced orange juice over the orange slices. Serve with some extra cinnamon sprinkled on top.