You can mark them as privat
What I actually meant is when I mark it private and select as free time, the slot still shows up in the shared view. In outlook, you can customize personal views that filter out certain types of entries (ie. private and free) however, when you share your calendar for others to see, can you set it up so that the same filtering occurs?
Unfortunately what you are asking for is not available in or native to Outlook, no.