Learning the clock is not an easy process for small kids. They can properly understand the mechanism only when they must start using it and getting a better notion of time. This rarely happens before 1st grade.
Here’s an easy version of an alarm clock, made from an old CD.
You will need the printable template, a CD, thick cardboard and a thumbtack or pushpin. Three of the elements (indicated in the template) must be made from cardboard if your clock is to stand upright.
Put the hands on the smaller cardboard circle and attach with a pushpin/thumbtack to the centre of the clock.
The base should also be made of cardboard, or else your clock will keep falling.