  Temporal broadening is a commonly observed property of fast radio bursts
(FRBs), associated with turbulent media which cause radiowave scattering.
Similarly to dispersion, scattering is an important probe of the media along
the line of sight to an FRB source, such as the circum-burst or circum-galactic
mediums (CGM). Measurements of characteristic scattering times alone are
insufficient to constrain the position of the dominant scattering media along
the line of sight. However, where more than one scattering screen exists,
Galactic scintillation can be leveraged to form strong constraints. We quantify
the scattering and scintillation in 10 FRBs with 1) known host galaxies and
redshifts and 2) captured voltage data enabling high-time resolution analysis.
We find strong evidence for two screens in three cases. For FRBs 20190608B and
20210320C, we find evidence for scattering screens less than approximately 16.7
and 3000 kpc respectively, from their sources, consistent with the scattering
occurring in the circum-burst environment, the host ISM (inter-stellar medium)
or the CGM. For FRB 20201124A we find a low modulation index that evolves over
the burst's scattering tail, indicating the presence of a scattering screen
$\approx9$ kpc from the host, and excluding the circum-burst environment from
potential scattering sites. By assuming that pulse broadening is contributed by
the host galaxy ISM or circum-burst environment, the lack of observed
scintillation in four FRBs in our sample suggests that existing models may be
poor estimators of scattering times associated with the Milky Way's ISM,
similar to the anomalously low scattering observed for FRB 20201124A.
