Here's where the hand tied bridal bouquets begin to take on a definite shape. Now you move on to carefully placing in the fourth stem. It is opposite the third stems, taking care to slide it in among the other stems carefully not to dislodge the pattern you have. After the grid begins to form, it will hold the later stems into place as you push them in with a little more force.
Here is a rough idea of how the stems look with four in a vase.
Top view shows how the flowers are casually opposite of each other. Don't expect perfection.