Lattice

  1. Press Shift+A and select lattice.
Warning

Make sure that the 3D cursor is set to the origin of the object.

  1. Resize the lattice so that it is SLIGHTLY bigger than the object on all the axis.
  2. Then first select the object and then the lattice.
  3. Press Ctrl+P and from the menu that opens, select Lattice Deform.
  4. Now select the lattice and hit TAB to go into the edit mode.
  5. Deform the object with the lattice.
Note

You can add edge loops to the lattice from the lattice menu on the side panel.

  1. Once happy with the result, you can select the object and apply the 'lattice modifier'. ( It adds itself as a modifier to the object )