The electric field can be thought of as an electric property associated with any point in space where a charge exists in any form. The electric force per unit charge is another way to characterize an electric field.
Therefore,
If the parallel plates of the capacitors are separated by a very tiny distance, the electric field can be made uniform.
When compared to the size of the parallel plates, the gap between the plates must be quite tiny.
Hence, this is the way to make a uniform electric field.
