Sea of green or sog= rooted clones put straight to flower in large numbers to achieve single cola'd plants
Putting straight into flowering or using a large number of clones are not required for a SoG.
A SoG is simply put a ScroG without the screen. With a scrog you bind branches down to a net, and usually remove everything below the net/screen, like in my previous halfpipe scrog:
The goal of a scrog and sog is very similar, getting an evenly divided leveled canopy, like I'm working on with my current SoG:

->
I do it by bending and snapping and pinching and even hanging weights on branches. An easier way to get a SoG is to use a rope net, like the WebIT from Secret Jardin, in which case you don't bind branches to the net but bend and push them below it to keep it all leveled.