Second side
Solve one side, turn the Clock over, then finish the other while keeping the first solved.
Flip method
Work on a visible face first, then flip the puzzle and solve the other while preserving the first. Align groups relative to a reference dial before moving them together to noon. The shared corner readings constrain both faces: redoing a finished group with the wrong pins can undo work on the back. Learn the pin transitions slowly before trying to turn wheels faster.