Preheat oven to 240 degrees Celsius.
Cut fennel into wedges about 2cm thick, and remove any green fronds and set aside for later. On a baking tray, toss together the fennel and orange slices with olive oil, season with salt and pepper and cook for 5 minutes.
Meanwhile season the salmon with salt and pepper.
Remove baking tray from oven and push the fennel and orange slices to one side, then place the salmon skin side up on the tray, and cook, on the top shelf of the oven for a further 8 minutes or until the salmon is cooked and starting to turn golden.
Remove from oven and scatter olives and any fennel fronds over the tray before serving.