This costume won't take a lot of time to make.
Parental supervision is recommended.
After measuring this, lay out flat. Cut out petal shapes out of poster board, leaving a small square shape at bottom of petal for attaching to the poster board strip that will go around the head. Staple the petals in-between the 2 layers of flower rings, making sure to start partway up on both sides, so as to have petals going around sides of face and top of head, but not under the chin. Staple or glue the ring after this to ensure sturdiness. Place it on the child's head, measure, but don't staple the ends until time to wear.