From a lateral view, you can see how the greens are taking on a dimensional look rather than a "flat" look. This is the proper way to green a bridal bouquet.
Begin making the center pieces shorter than the outer greens. Again, these center insertions should stick straight out of the middle.
Don't try to fill in the fern too tightly. You will want to cover up the mechanics, but you have two other varieties of leaves and then the flowers to insert.
Continue until the bouquet is greened in completely and has a nice oval shape from the side view.