It's arranged in lines of 8 assemblers for convenience, each line of 8 requires: 1 copper wire assembler, 1 green circuit assembler, <1 plastic chem plant (=1 if all yellow assemblers).
I haven't done much of the math about this setup, but I'm certain that the copper wire transport belts need to be red belts or better. You can probably get away with yellow belts everywhere else to make the setup (alot) cheaper. Basic inserters are also acceptable instead of fast ones.
- it's nearly 100% space efficient, except for the exterior belting, every space is used.
- it can very easily be expanded with the use of blueprints.