For an 8x8 space for 3 hens (if you can stick with 3) I'd consider an elevated coop that's 4x4 inside an 8x8 run. Reason for the measurements is because lumber generally comes in 4' increments, so this can help minimize cuts and waste. In FL you will want a LOT of ventilation.
OR
Another option to take advantage of your climate would be an open air set up, where the coop and run are combined into one space. So the entire 8x8 would serve as both. The chickens really just need an area with a roost and shelter from winds and the elements. A fully enclosed wood "box" shouldn't be necessary in your environment. Lots of examples here of fully open and partially open set ups:
https://www.backyardchickens.com/threads/wanted-open-air-coop-pics.1489579/