A hearing instrument and method of assembly are disclosed. The hearing instrument comprises an electronic assembly for providing received sound to the ear canal of a hearing instrument user. The electronic assembly is placed within a chamber in a housing sized to fit within the ear of the hearing instrument user. The chamber includes an internal guide channel and mounting surface for locating and positioning the electronic assembly. A volume encompassed within a hearing aid housing may be analyzed, such as with computer software, to identify a location within the chamber to position the electronic assembly, and then the electronic assembly may be incorporated into the housing using a guide channel and mounting surface of the housing for locating and positioning the electronic assembly in the identified location.