Composite flowers are time intensive and should be done on the day of the wedding. Some type of collar is advisable to give this delicate design more support. You can cut out a circle of cardboard and either staple or glue the salal leaves to it, then finish by adding more salal leaves still on the stem to create a longer bouquet handle.
To create this look, you'll need the following hard goods and fresh flowers:
If you need a detailed composite flowers tutorial, it is wise to watch this video first. It's not terribly complicated, but you have to take care in handling the flower petals and using the right flower adhesive. Hot or Cold melt glue can harm the rose petals and becomes brittle when refrigerated (which is a must with this type of bridal bouquet).
If you need more help on constructing a round collar from cardboard, check out the English Bouquet Tutorial.