Some hardy annual seeds can be sown now. If you like a natural look simply scatter seed directly where you want them to flower and cover with a fine layer of soil. This is the quickest method but identifying the emerging shoots from weed seedlings can be a bit difficult.
If you prefer a more structured planting, divide the bed into sections and sow in shallow drills running in different directions to achieve a natural look. It is easier to spot the young seedlings from the weeds between the drills. Cornflower, Love in a Mist, Poached Egg Plants (Limnanthes), Iceland Poppies and Marigolds (Calendula) are all suitable.