First, clear the acorns surrounding flowerbeds so that the stream can start making auto-matches, thus helping you grow and gather more flowers.
Then, start clearing the sides of the field, creating bombs and clearing the layers of grass. Combine your power-ups so that your Rainbow Blast charges faster; it will save you moves.
After you've collected all the gnomes on the sides, return to the flowerbeds. Each 3 matches or explosions next to a flowerbed make it produce 4 flowers on the field. However, it’s best to let the flowers fill up the field first, and then collect them with a Rainbow Blast.