I like the idea of a template. That will make the pieces very consistent with each other and will make it easier to assemble. You probably already know this but if the height and width of the cabinet storage area are not the same, you will need separate templates for the horizontal and vertical boards. Also, the slots need to be just slightly deeper than 1/2 of the depth (front to back) of the grid. That way they can be inserted fully into each other.
Good luck with the project. It looks like a good one.