Carnations are a good choice for church flowers, since they come in a wide variety of color and have very long stems. If I use spray carnations instead of standards, I tend to mass them in the design for more effect.
You can see how I placed the first stem directly in the back and center of this floral, using all the flower heads on the single stem.
If you cut some in half, you can use the shorter portions in the center and front of the design.
Work your way down the flower design, mixing them among the snapdragons and making sure the flower heads extend beyond the greenery for best effect.
Alternate the sides and distribute the flowers evenly.
I cut some of the stems in two pieces. Don't mistakenly discard the tight buds, these will open in time and even the buds alone add a lot of interest and texture to your bouquet.
The shorter stems can be place in the center of the flower design and tilted slightly forward.
The contrast of the lighter flowers against the dark leaves helps them stand out in a floral.
Work with the natural curve and droop of the flowers to emphasize the lines of your bouquet.
I still have more carnations to place in this floral, but you can see that it flowers in rather quickly. You can even transport your greened pieces to the church and finish flowering once you are there.