So, what you’ve run into here is a thing called the hackbox. And we do actually have quite a lot of guides that mention it, both for Builder use generally and for portrait-making specifically, but with the sheer volume of resources out there (some of which are uh. not as good as others) and the amount of stuff covered in said resources, it can be easy to miss. I cover it in this post of my FEBuilder FAQ here:
That post also talks about the exceed hackbox patch, a way that you can get some of that space back! It’s a really useful patch, though still somewhat restricted.
In terms of tutorials to look at more generally, my FAQ is at this point the primary and most comprehensive FEBuilder reference source around – it’s linked in Builder itself as the online manual, having taken the place of its original docs, and I can say with reasonable certainty that most questions new users will have are answered in it somewhere. That said, it admittedly can be hard to navigate if you don’t know what you’re looking for – it’s written as a series of answers to specific questions and problems, made to be searched when you’re stuck, moreso than a structured tutorial. For a more structured long-form tutorial, I can also recommend Parrhesia’s “How to Excel at Builder Without Being Good At It”, which is a proper beginner’s guide and probably the current best overall place to start when new.