The extreme confinement and directional propagation of polaritons in highly anisotropic van der Waals materials have recently opened new opportunities for nanoscale light control. In particular, these materials can show canalization – a regime in which polaritons propagate along a well-defined direction with strongly suppressed transverse spreading. However, canalization has so far been explored mainly as a fundamental phenomenon, while its potential for realizing nanophotonic elements has remained largely unexplored. Here, we experimentally realized a Fabry-Pérot-like nanoresonator in a single α-MoO3 layer on a gold substrate, where canalized hyperbolic phonon polaritons (HPhPs) are launched and reflected by two compact scatterers (nanoholes), producing resonant confinement along a well-defined direction. This result shows that canalization can be harnessed to create “virtual” waveguides and resonators in an otherwise laterally unpatterned heterostructure, providing a route towards enhanced light-matter interaction. Building on this concept, we develop an analytical quantization framework for canalized HPhPs and predict bound states in the continuum for emitters coupled through an α-MoO3 layer on a negative-permittivity substrate. Our results identify canalization as the key ingredient that renders the polaritonic environment effectively one-dimensional, enabling strong emitter-emitter coupling in virtual waveguides without geometric confinement. These findings establish highly anisotropic media as a promising platform for polariton-mediated quantum interactions, with potential applications in quantum optics and integrated quantum photonics.