Use a small, sharp knife to top and tail the oranges. Cut down the sides of each orange, following its natural curves, to take off the skin and pith.
Holding the orange over a large bowl (to catch the juice), cut in between the membranes to remove the individual segments, discarding the membrane and pips as you go; break up the segments slightly as you add them to the bowl. Add the lemon juice, oil and a teaspoon of salt, and toss to combine.
You can make the salad in advance up to this stage but don’t add the remaining ingredients until just before you want to eat.
Once everything is in the bowl, toss again gently, transfer to a large platter or individual plates, and serve at once.