Making an asymmetrical flower arrangement is my favorite because you can easily hide flaws. You will want to make one side heavier than the other. Start with your greenery having more stems on one side. Still add 1-2 stems on the other side, but make them a bit shorter. Fill in your flowers and make the stems longer on one side. Add in floppy/whimsical flowers like veronicas to add in more dimension and layer up on one side more than the other.