This is what I came up with to fully supply a single green circuit plant:
Unfortunately, two stack inserters are required for cable insertion from the plants that only have a single tile facing the circuit plant. With only blue inserters, production is 10% lower or about 80/minute.
You can tile and mirror it, although a single setup requires 450 copper per minute, so it you tile it you need more copper than a single yellow belt. If you tile it twice, however, and don't use stack inserters you more or less consume the full copper belt. If you tile and mirror it you consume close two two belts of copper, (less than) one belt of iron, and produce just under half a belt of circuits (320/minute):
mirrored and tiled without stack inserters
of course, when you get the better tech the stack bonus or stack inserters will take over. With yellow assemblers a single green circuit will consume 750 copper, so upgrading the copper belt to red and the plants to yellow you can more or less double production. With a blue belt of copper you can add a third unit, but then you also get into productivity module territory which changes the ratios again (to 1:3.5, nice challenge finding a setup for that 
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