Buy a clock mechanism from a craft store.

Pull the hour and minute hands off ... carefully.

Make a long minute hand with a white circle at the end from manilla folder cardboard and a shorter hour hand.

Hot glue your hour and minute hands onto the clock hands you just removed.  Be careful not to cover the mounting holes on the clock hands.

Press the hands back on the clock.

Screw the clock into a piece of soft wood.  (Bass wood and four 1" wallboard screws at the corners usually work well.)

Mount the light sensor so that the red light shines on the white circle of the hour hand.

You can set the time by carefully turning the hour hand.

Mount the RCX programmable brick at the bottom of the basswood piece.

Screw the Bass wood piece into the wall.