This isn’t going to be hard.
Take one whole sea trout. Roast it at 200C/400F until just cooked at the shoulder. (you can tell by prying the flesh apart with the tip of a knife and looking). Don’t overcook it. Rest for 5 minutes. Eat it.
You don’t need to season it, herb it, or otherwise mess around with it. Reason being, sea trout was created by angels and raised by gods. Therefore it is perfect.