It does help to plan when you are doing free piecing, or at least have an idea of the general shape you want to finish with - a house, a flower, a star. Quite often I actually make a sketch if my brain is baby addled and I can't figure out how the pieces should go together. (I should share my sketches one day - if a quilt block could be a stick figure then I am an expert at drawing that!)
Free piecing in this context is about the process of cutting and piecing. There are no templates and often no rulers when cutting. Sewing is just one piece to the next. You often start from the inside of the block and work out. You have the be creative and improvise along the way. For example, in the house block above I didn't cut a piece long enough to encompass the angle of the roof. That means the roof doesn't overhang the house that much and the roof is smaller than intended. Oh well. I compensated by adding another strip of the background fabric to make the block big enough. Problem solved.
This technique also works well in combination with freely cut applique pieces, like this artist.