Although modern software has paved the way for architects to design complex forms, such as free-forms, construction remains challenging, costly, and time-consuming which requires skilled workers. Advanced digital fabrication technologies can offer new ways to fill the gap between design and construction. Augmented Reality (AR) technology is one such technology that has many potentials in various fields, however, its capabilities are not sufficiently explored yet, especially in the field of digital fabrication. This study presents a new affordable interactive multi-marker augmented reality tool for constructing free-form modular surfaces implemented by integrating common accessible devices. The proposed tool consists of two digital cameras, a head-mounted display, a processor, and two markers that enable the user to virtually see the accurate location of any proposed object in the real world. A controlling subsystem was also designed to enhance the accuracy of construction. Method efficiency was studied in five full-scale prototypes. The results showed that the majority of errors (91%) were less than 6 mm, and 2° for lateral placements and orientation errors.