Place the agapanthas stems into the floral foam at different angles, so it looks like the fireworks are flying in different directions. If you can’t find agapanthas, look for other flowers that are large and spherically-shaped, like hydrangeas. The great thing about agapanthas, though, is that much of the fllower consists of thin stems, which resemble the trajectory of fireworks.
Helpful hint: As the days go by, this arrangement will stay fresh, but individual buds of the agapanthas will wilt. Just pluck off the offending buds. The fireworks look even more realistic when the agapanthas are a bit more sparse.