Intercalation of air-stable monolayer Pb into EG/SiC by confinement heteroepitaxy (CHet) enables study of heavy metal films at the extreme limit of thinness with complementary microscopy and spectroscopy. Pb coverages up to 90% can be achieved at elevated temperatures beyond those of conventional ultrahigh vacuum methods. CHet-based Pb exhibits a Frenkel- Kontorova domain boundary network due to lateral compressive stress relief within a (1 × 1) Pb/SiC model, which can be seen experimentally as a (10 × 10) superstructure. Anticipating a large spin polarizability, we leverage uniformly intercalated Gr/Pb/SiC as a basal layer for a ST-FMR measurement, discovering a 1.5× increase in the effective field ratio over a hydrogenated sample and consistency with C3v symmetry. Intercalation of Pb in EG/SiC is thus a promising material platform for ex situ spin transport phenomena.