The second product that boards produce are explicit governing policies. These governing policies reach only as far as the board is concerned about having their hands in it.
If the governing policies are too deep, the board will become swamped in fulfilling the means. Any board that does not understand means vs ends would do well to study and explore that topic very deeply. Additionally, when boards become involved in the means they end up micro-managing and doing the job as opposed to developing the policies for those that do the job.
On the overhand, if the governing policies are too shallow then the board has given too much authority with regards to the 'how to' that the senior employee can use to achieve the outcomes. Doing so puts the organization at risk financially, morally, relationaly, etc.
Boards do not do the job. They develop the governing policies for those that do the job (or better yet, only for the senior leader).