Both baking and frying meatballs before adding them to a stew can work, and each method has its benefits. Baking is generally less hands-on than frying. You can place all the meatballs on a baking sheet and cook them at once without turning them repeatedly. Baking ensures that all the meatballs are cooked evenly and to the same level, which can be harder to achieve with frying. Frying can create a more flavorful meatball and savory flavor. Also, frying provides a crispier exterior to the meatball, which can provide a nice contrast to the soft interior. If you prefer a lighter meatball and easier method, baking is a good choice. If you like a richer flavor and don't mind a little extra work, frying could be the way to go. In either case, browning the meatballs before adding them to the stew will provide a depth of flavor.