Making separate meshes are probably your best option. That is one mesh for the clock, and one for each hand. It is very important to make the center of the hand the point that the hand should rotate around.
The alternative is to make it a skeletal mesh with each hand assigned to a bone.
The cons and pro's of both are:
Static meshes
+ Easier to use
- More draw calls
Skeletal mesh
+ Less draw calls
- Harder to use
There's also a third option, to animate the clock using shaders. Would not recommend.