US Stock Asset Allocation by Style+Sector

If we break up stocks/ETFs by style (large, med, small) x (value, blend, growth), we will have 9 combinations. If we break up stocks/ETFs by sectors, we will have around 10 sector combinations. How do you balance this 9 x 10 two dimensional stock asset allocation manually? I know PersonalCapital or other Robo advisors do this. Do you care to diversify this much? or just by sector or just by style or both? Please advise on the right mix to focus.