This might be stating the obvious. but I have to say this as it may be something that will not occur to some people.
I have spent hours trawling the internet for free templates for boxes of different shapes and sizes. When it would have been quicker to look through my kitchen cupboards at the food packaging.
Oxo and Bovril boxes are a great templates for small boxes, I also found the box the vet gave us with Stan's medication in (after his encounter with a squirrel ) made a great template too. Now when I go shopping I find myself eyeing up the packaging to see if it has potential as a template .