Look closely from the sides to fill in the open spots of your bouquet.
Covering your mechanics in an important rule in flower design. Unless the mechanics are a part of the design (such as colored wire), always make sure tape, wire and foam is completely concealed from all angles.
You need to view your bouquet from the sides and tops - not just from the front.
I'm tucking in some purple carnations in the sides to give contrast in color and different texture than the gladiolus and the hydrangea bloom.