For using volume measurements (weighs are still superior tho) flour shouldn’t be packed in but spooned into the measuring device and leveled with the back of a knife but brown sugar should be packed into the measuring device.

In recipes, they’ll call for a heaped teaspoon or tablespoon, everything else is implied to be leveled, especially leavening agents like baking powder/soda. There’s also an understanding that certain things don’t need as much precision, like adding in flavoring extracts.