At its best:
Jun, Jul, Aug
If you're using a metal container, line the sides with cardboard to prevent it from heating up and drying out the compost.
Half-fill with multi-purpose compost and add gravel for drainage.
Plant up the centre of the container with dahlias and cosmos, and the front and sides with cerinthe.
Backfill with compost, and firm gently to remove air pockets. Water well and place in a sunny location.