The present technology comprises methods of manufacturing an orthodontic appliance. For example, a method can include forming an orthodontic appliance in an intermediate configuration by a casting process. The method can further include securing the appliance to a shape forming fixture such that the appliance assumes a desired configuration. The shape forming fixture can comprise a gingiva portion including a surface having a shape corresponding at least in part to a gingiva of a patient and a securing portion carried by the gingiva portion and configured to releasably secure to a portion of the appliance. The method can further include setting a shape of the appliance while the appliance is secured to the shape forming fixture.