I have a detailed box set tutorial that I have been putting together for a long time now. I just haven’t posted it because it’s not 100% complete. However, your post has inspired me to work on it again. Maybe by the end of the week I can have it ready to post.
I will say this, it does take lots of measuring and re-measuring. I have even held up my artwork to the box to double check the alignment.
I would also suggest using something heavier than cardstock. I use matte board from a art store; it’s heavy and durable and looks great when completed.