C-4 looks like a stinker to make.
The inside lattices finish to 1/4 inch.
If you are a beginner, it will be an interesting learning experience for you.
Definitely get templates. And check your dimensions at each stage. If the templates match the book, the dark pieces in the center are different sizes - the four corner ones match, the center sides match, and the center is different.
I managed to draft it to look almost like C-4 in the Dear Jane book.
I'm wondering if Jane made the center first and drew the rest around it. The grid is uneven in the book - hard to draw 5/12" blocks - those would have come out "even"