Incompetence. You don't need to be able to do everything. You hire employees to take care of your tasks for you. You don't need to be competent when you can offload responsibilities onto others. If you have no desire to do a task or don't even know how to do it, don't worry about it. Just make someone else do it.
Ignorance. Closely related to intentional incompetence is willful ignorance. You don't need to know everything. It's the employee's job to know how to do things. They are getting paid for their knowledge and labor so that you don't have to waste your precious time doing sundry tasks. Focus your energies on giving orders and controlling the flock. Don't waste your time learning about things when you're just going to order someone else to do the work.
Inconsiderateness. You could be nice to your employees. But I don't subscribe to that silly line of thought. You are the boss, and they are your underlings. You should remember that there is a clear hierarchical power structure. You are are higher up the chain, so order around and take advantage of your underlings at will. It's your duty to get maximum effort from your workers, not to be buddies with them.
Infrequency. How often should you need to do actual work? Ideally, never. But since it's not an ideal world, you probably will have to do some real work every so often. Keep those periods to a bare minimum though. Fill your time doing stuff that you want to do. Leave the dull work stuff to your underlings. They are paid to work so that you don't have to.
As a bonus, here is one more I to keep in mind: yourself. Being a PHB means that you should be most concerned with número uno. Your actions should be driven by self-interest above all. Keep the fifth I at the forefront.