There is no real world flat surface which goes on forever. It is a geometric idealised concept. So, since there is not even a first such thing, there cannot be another.
A flat surface that extends forever is a plane
A plane.
Plane
Plane
lever
A flat surface that extends forever is a plane
A plane
A plane.
A plane
A plane
Plane
A plane.
Plane
a plane
lever
A floor.
A face is a specific side of a three-dimensional object, while a flat surface refers to a surface that has no curves or bumps. All faces are flat surfaces, but not all flat surfaces are faces on a three-dimensional object.