There can be no such shape. If there were a shape with n flat surfaces, then if you sliced off one vertex, you would have a shape with n+1 flat surfaces. So it is always possible to add one more flat surface.
a cylinder l
A sphere
a rectangle
cube There are a great many solid shapes that have only flat surfaces.
A cube
A cylinder
It is a cube or a cuboid
cylinder
Cylinder
A sphere
A sphere