If you're developing a Flutter UI with any complexity at all, understanding layout basics such as padding, viewPadding, and viewInsets is critical.
In this article, Lê Dân gives us the details on these concepts in a nicely-illustrated overview.
In reviewing this article, I also appreciate the fact that Dan's medium profile lists several Flutter-UI-related articles. Topics include intrinsic size, SliverAppBar, and managing a widget's visibility. I think these are very worth checking out, especially if you'd like to build your foundation in these basic but important topics.