After reaching Aerith’s house in Chapter 8 she’ll force you to pick three types of flowers. Pick whatever you want three times (even if you pick the same flower multiple times) and take the flowers to Leaf House. Advance the story (and optionally complete some side quests) and when you’re heading back to Aerith’s house you’ll be shown what has been made with the flowers you picked. The arrangement varies based on the flowers you selected earlier, but for this trophy the outcome doesn’t matter. Cannot be missed.