You could lay the tile right up to the base of the toilet, but that will require a lot of fancy tile cutting and you would be SOL when you later try to replace your toilet with a new one that is not likely to have the exact footprint of your current toilet.
Best thing to do is remove the bowl and set tile on the floor around the flange. You may need to raise the flange. or may not.
Take toilet up and the tile has to be under the flange . You can try to set bowl without raising flange if your tile is not to thick. If it is and you dont want to raise flange then go to Plumbing supply house and get a flange extender, it is another flange about 1/4″ thick you put on present flange. I just wanted to give you the facts, what ever way you do it put the new tile under the bowl.