How does a CEO or corporate excecutive hedge a large single
stock portfolio (that single stock being shares of their own company)?

I suspect he is limited in hedging that is practical, if the single
stock represents nearly all his assets.
 He can put in a limit order to sell all or part of his stock if the
price drops by perhaps 10%, but this creates some ethics problems,
especially if the stock sells minutes after he puts in the order. I
suppose calls, puts, and derivitives have some hedging value, but I
don't know any details.
 Diversifing the company by mergers, purchaces and other aquisitions
tends to make the stock less changable in price.   Neil