How to cook sea bass fillet in foil in the oven from frozen
Simply make a tightly sealed parcel of the foil by doubling it and folding over the fish and sealing the edges. I'd include some knobs of butter and lemon slices, and some fresh ground pepper.

As for cooking time, that really depends on the thickness of the fillet. I would say around 20-25 minutes at 180°C/350°F as a guide, but you should make sure the fish is piping hot throughout and opaque white with no translucent bits.