300 layers x MINIMUM standard of 4 sq ft per bird = 1200 sq feet of floor space MINIMUM. 900 sq ft won't cut it,IMO, regardless of how you break it up.
This is why cage farms are the egg industry standard - it costs a lot more to house hens in a more open setting as more space = more money. Trimming the beaks and cramming just a couple birds in separate cages that you can stack reduces losses and stress due to picking, the size of the barn needed, and makes it much easier to automate feed/water and collecting eggs.
Also the 4 sq ft is a MINIMUM. I can tell you that if you cram 300 laying hens in a 1200 sq foot coop, you will have some mighty stressed hens with the constant pecking order squabbles, fights over nest boxes, etc. You will have to have superb husbandry practices as well to keep your flock disease free and healthy. With that much density you are asking for a mass health problem.
This why standard eggs cost about $2 a dozen and cage-free at least 50% more, and 'Free Range" even more than that.
I urge you to rethink your numbers, or your strategy for the sake of the hens, and your own bottom line. Personally I would not put many more than 100 hens in that size of coop, (8sq ft per bird) and that's if they have an area to free range.
I have 20 hens in a run about 20x80 (1600 sq ft) and I can't imagine having more than about 20 more hens in there and still having a peaceful and healthy/happy existence for them where they can do their natural chicken behaviors.
