Methods of fabricating a base layer circuit structure are provided. One fabrication method includes: providing an alignment carrier having a support surface; forming a plurality of electrically conductive structures above the support surface of the alignment carrier; disposing a structural material around and physically contacting the side surfaces of the electrically conductive structures formed above the support surface, the structural material having an upper surface coplanar with or parallel to the upper surface of one or more of the electrically conductive structures; exposing, if covered, the upper surfaces of the electrically conductive structures to facilitate electrical connection to the structures; and separating the alignment carrier from the base layer circuit structure. The base layer circuit structure includes the plurality of electrically conductive structures and the structural material surrounding and physically contacting the electrically conductive structures.