Cut the foam block with a paring knife to fit inside the round vase or dish. Cut off squared corners to create a round shape. The foam should stand 1 inch above the edge of the container.
Make 6 "X"-shaped knife cuts in the top of the foam block. Twist slightly with each cut to create wide openings. This allows water to easily soak deeply into the center of the foam. Add water very slowly to the oasis, especially into the "X"-shaped holes. Soak for 10 to 20 minutes.
Choose taller flowers with strong stems for the center of the arrangement. If the stems are not strong, wrap them loosely with wire before using. Tall flowers such as delphinium, iris, hybrid tea roses, lilies or tulips make an attractive arrangement center.Cut stems to create a balanced height with the size of the bowl or vase. Press the stems firmly 1 or 2 inches into the soaked foam.
Choose medium and smaller flowers to create a pyramid shape of flowers from the center. Flowers with many individual blossoms such as lilac and hyacinth fill the visual space effectively. Press their stems 1 to 2 inches into the foam. Use all the flowers, creating a look of loose abundance or formal elegance. Fill in any remaining spaces with fern leaves or baby's breath flowers.