Thinking begins in your mind. Thinking is the process of using one’s mind to consider or reason about something. Typically thought is constrained by pre-defined concepts.
That is, you need something to think about and normally that is already defined. Based on the already known concepts you use reasoning to develop an understanding that goes beyond, or perhaps just validates what is know.
Unconstrained Thinking
Given most thoughts begin on the foundation of an already recognized concept truly free thinking is difficult to engineer. In essence the thought process begins from nothing.
There is no starting point or beginning. Thinking without reference or conceived understanding of something is the most innovative and creative.
As there is no defined starting point or goal, free form thinking almost needs to start from a point of unconscious awareness (two contradictory concepts).
Manage your Thoughts
While you can use your mind both consciously and unconsciously, control of the process typically requires some conscious oversight to be a fully formed idea you can act on.
To avoid constraints, migrating the idea from your sub-conscious to
Unfortunately our conscious minds apply pre-conceived constraints, assuming they are valid, which causes ideas which do not conform to known concepts to be cast aside arbitrarily.
Unconstrained thinking does not always lead to results but if you shut ideas down without some thought, good things can be overlooked.