Summarize the following:
Make sure that the oven is completely heated before baking the plaice fillets. This will ensure that they cook correctly. A medium sized gratin dish works best for 4 fillets. Make sure that there is enough room for each, and that they are not overlapping at any point. Use a light coating of oil or butter to cover the dish. Baking paper also works well and reduces the mess to clean up afterward. Combine the lemon juice, chopped parsley, flaked almonds, and olive oil to make a salsa-type dressing. The time depends on the size of the fillets, and how cold the ingredients are to begin with. When the fish is cooked through, remove from the oven and leave resting for 1 minute, before transferring onto a serving plate. You can tell that the fillets are cooked through when you make an incision in the middle of the fish, it looks opaque, rather than translucent like when it's raw. Cooked fish will also easily break into flakes when it's done.
Preheat an oven to 180C/356F/gas mark 4. Place the fillets in an ovenproof dish. Season the fillets in the oven dish. Bake the fillets uncovered for 10-15 minutes.