A stock instrument includes at least one guide interacting feature. A lower instrument surface of the stock instrument is placed into contact with the patient tissue. A guide has a lower guide surface contoured to substantially mate with at least a portion of an upper instrument surface of the stock instrument. A predetermined instrument orientation upon the patient tissue is defined, which is preselected responsive to preoperative imaging of the patient tissue. The guide and instrument are mated in a predetermined relative guide/instrument orientation wherein at least one guide interacting feature of the instrument is placed into engagement with at least one instrument guiding feature of the guide. The guide is moved into a predetermined guide orientation with respect to the patient tissue and concurrently the instrument is moved into a predetermined instrument orientation with respect to the patient tissue.