You will need to sex them then plant them about 6 inches apart in any patern you like as long as they are close together.
Also I would make sure that strain you have will do well in the sea of green method NOT ALL STRAINS WILL THRIVE IN THIS METHOD IN FACT IN SOME STRAINS YOU WILL REDUCE YOUR YIELD GREATLY.
Hope that helps ya
Google Marijuana+Sea+of+Green. There are tons of how to's.
SOG flowering rules:
1 plant in flower per square foot
no topping just LST
Trim lower shaded branches to allow the plant to use its energy in the main cola.
Find a good mother plant and use clones
Tough love is kind of the approach when delaing with pruning, especially in SOG type stuff, the last thing you want to do is cut off the stuff you've trying to make go. Like a fruit tree, you can have a bunch of mediocre ones that are getting shaded and taking up juice, or some bitchin' ones on top/middle.