Swirling a seam helps to reduce bulk at the intersection of four or more fabric pieces.
First, identify the seams perpendicular to the one just sewn – the arrow below shows where they are.
Unpick the outermost three or so stitches from these seams – those that lay within the seam allowance of the seam just sewn.
Once these stitches are removed, the centre point seam where all four blocks meet will be able to “fan out” around the centre point, greatly reducing the bulk of this intersection.
The seams that radiate out from the middle will also fall naturally in the same direction (either clockwise or counterclockwise).
Once your seam has been fanned, press the intersection and seams to set it in this configuration.