I had a book for this when I was a kid, but since I lived in Europe, all I had was A4 format paper and most models were for Letter or folio format!
Obviously the book was translated from US.
I don't remember how bad it was in practice but I remember it made me sad.
Was getting your parents to explain proportion and take scissors to a sheet not an option?
Interestingly, paper A4 wide (210mm?) by letter tall (11") is a thing in the TeX community.
How I felt not having square origami paper as a kid.
(It's okay, I learned immediately how to rectify, uh, squarify, the situation.)