Mix the olive oil with a full teaspoon of all-purpose seasoning. You can also use other oils and simply season with salt and black pepper, or add dried herbs, paprika, or soy sauce if desired. It should have a salty and optionally spicy flavor.
Toss the halved Brussels sprouts with the oil in a bowl (or in the baking dish), preferably by hand.
Place in a baking tray large enough so they are not stacked on top of each other and bake at 180°C for about 30 minutes.