You either utilize one of the stock layout managers, which place the Fields according to their design (like HorizontalFieldManager or VerticalFieldManager, etc), or you utilize a combination of these, or you write your own custom layout manager.
Although you can place fields at a particular x-y position using your own layout manager, this would probably not be considered "best practice".
Perhaps if you explain what type of layout you are looking for, someone may be able to suggest a method of accomplishing your goal.