I claim the ornamental design for a three section foldable clipboard, as shown and described.
FIG. 1 is a perspective view of a three section foldable clipboard in an unfolded position;
FIG. 2 is a perspective view of the three section foldable clipboard with a first and third section folding toward a second section;
FIG. 3 is a perspective view of the three section foldable clipboard in a folded position with the third section folded over the second section and the first section folded over the second section;
FIG. 4 is a top plan view of the three section foldable clipboard in the unfolded position;
FIG. 5 is a bottom plan view of the three section foldable clipboard in the unfolded position;
FIG. 6 is a right side view of the three section foldable clipboard in the unfolded position;
FIG. 7 is a left side view of the three section foldable clipboard in the unfolded position;
FIG. 8 is a top plan view of a lower end of the three section foldable clipboard in the unfolded position; and,
FIG. 9 is a top plan view of an upper end of the three section foldable clipboard in the unfolded position.