Thanks everyone. I've got prior die cuts that I'm working from. I'm looking at the "Book of Patterns." I ordered "Innovations and Ideas" from the Paperboard Packaging Council.
What's perplexing to me are folds. How do you measure the outside face of a box, versus the inside and how do you account for the width of the fold. It's kind of a mathematical hell for me. If I just had some guidelines. Also, these are Self-Locking Trays made with a very thin fluted board (corrugated).
I'm actually working on the inner packing to keep the materials in place. It just seems that certain faces need to be a bit shorter than others to accommodate for folds, like by a mm.
Any guidelines, formulas, rules of thumb would be appreciated.