The next ORK 3 update will also add some new features to make things easier. You can 'create' a new item box by adding the component to a game object with the new Create Item Box node and the Get Combatant Gains node allows storing the loot in item boxes (either via box ID or using a game object's Item Collector) or selected data.
In short, you can e.g. turn the dead combatant's prefab into an item box and add the loot to it (if you don't destroy their prefabs). Otherwise just spawn a prefab and use that.