As an action, a hammer appears in your free hand and lasts for the duration. You create the hammer as a magical club, greatclub, hammer, mace, maul, or warhammer.
The spell ends if you dismiss it on your turn (no action required), if you cast it again, or if you end your turn without the hand in your hand as the hammer dissipates.
At higher levels
When you reach 9th level, you can make an attack with the hammer as part of the same action to create it.