Lay a large sheet of baking parchment on a baking tray. Place the coriander on top of this.
Cut the orange into slices, then lay these on top of the coriander. Place the fish on the orange slices.
Slice the ginger into 0.5cm slices. Lay these on top of the fish.
Drizzle the sesame oil on top. Add a good pinch of salt.
Wrap the baking parchment around the fish so that it is fully covered (you can use a second piece of parchment if you need to). Put the fish in the oven for 30 minutes.