Complete the account of what a dielectric does to a field.

A dielectric weakens the field inside it, because its bound charge sits antiparallel to the free charge and partly cancels it. The reduction factor is the relative permittivity, which for an ordinary material is always greater than one.

Polarisation puts bound charge on the slab faces opposing the free charge, so the net field falls by $\varepsilon_r = 1 + \chi_e > 1$. This is also why filling a capacitor raises its capacitance by the same factor.