Optical assemblies may include a projector assembly and a waveguide assembly. The projector assembly may include at least one light subprojector and a housing including at least one receptacle. The waveguide assembly may include a waveguide and a waveguide holder. The housing may include at least one receptacle and the waveguide holder may include at least one support leg. The support leg may be positioned within, and secured to, the receptacle to align the projector assembly with the waveguide assembly. Related head-mounted displays, systems, and methods are also disclosed.