Ostomachion

Ostomachion (στομάχιον), also known as loculus Archimedius or syntomachion, is a mathematical treatise attributed to Archimedes. It is the oldest known mathematical game. The game is a 14-piece dissection puzzle forming a square (other forms are also possible). Bill Cutler showed that there are 17152 solutions to form a square. But if you dismiss equivalent solutions under rotation and reflection, you end up with 536 truly distinct solutions. See: https://en.wikipedia.org/wiki/Ostomachion

I plotted them here in a 27x20 grid so four places are left empty.