  van der Waals nanomaterials supporting phonon polariton quasiparticles
possess unprecedented light confinement capabilities, making them ideal systems
for molecular sensing, thermal emission, and subwavelength imaging
applications, but they require defect-free crystallinity and nanostructured
form factors to fully showcase these capabilities. We introduce
bottom-up-synthesized {\alpha}-MoO3 structures as nanoscale phonon polaritonic
systems that feature tailorable morphologies and crystal qualities consistent
with bulk single crystals. {\alpha}-MoO3 nanoribbons serve as low-loss
hyperbolic Fabry-P\'erot nanoresonators, and we experimentally map hyperbolic
resonances over four Reststrahlen bands spanning the far- and mid-infrared
spectral range, including resonance modes beyond the tenth order. The measured
quality factors are the highest from phonon polaritonic van der Waals
structures to date. We anticipate that bottom-up-synthesized polaritonic van
der Waals nanostructures will serve as an enabling high-performance and
low-loss platform for infrared optical and optoelectronic applications.
