Launch an app that uses the onscreen keyboard, like Mail, Messages or Notes. Tap an editable text field if the keyboard doesn't open immediately.
Tap the "Keyboard" key, which is located on the bottom right of the keyboard, to hide the keyboard. The key has a picture of a keyboard on it. That's all you need to do -- the keyboard is now hidden.
Tap an editable text field on the screen to launch the keyboard again.
Tap and hold on the "Keyboard" key and select "Split" to split the keyboard in half or "Undock" to allow the keyboard to move up and down on the screen with a touch and drag on the Keyboard key.