The diameter of the Earth at the equator is 12,750 kilometers, and the distance between the poles is 12,712 kilometers. So the flattening is very small indeed. The Earth is commonly compared to an orange in shape; but an orange of exactly the same form as the Earth would appear to the eye to be perfectly spherical. Assuming the orange to be three inches in diameter at its ‘equator’, its ‘polar’ diameter would be only one hundredth part of an inch less than three inches.
So, it’s okay to say that the Earth is spherical.
Flat Earth (Wikipedia)