Flip them over to flower when they're 10-12 inches tall or do a scrog - put a screen about a foot above the plants and when they start growing through, weave them between the holes until your screen is about 40% - 60% full, then put them on 12/12 where they'll start to stretch, continue weaving until the screen is full and sit back and enjoy. You may want to trim under the screen since there isn't going to be enough light getting down there and it'll make it a little easier to do things like water.