A flat clinch assembly fits upon or within a base of a stapling device. The assembly preferably includes a slot with extended resiliently biased arms or toggles, where a rest position has the arms at or near a level of a working surface. An ejecting staple deflects and energizes the arms to cause the arms to rotate and create a clearance recess whereby points of the staple legs slide inward along the anvil. A restorative bias acting on the arms causes the arms to rebound to a rest position and to bend the legs upward. The legs thereby are normally pressed flat against the back sheet of a paper stack at the working surface. The arms or toggles are lightweight whereby the inertia of a fast moving staple moves the arms or toggles.