We verified experimentally a new method of development of well know D-shape fibers. Instead of mechanical or chemical postprocessing of standard fibers, we have developed a D-shaped preform and further processed it on a fiber drawing tower Inversion of the fabrication process allows to obtain hundreds of meters of uniform sensing fiber with a thermodynamically flattened sensing surface. We have developed fibers with a core of 7 by 8 µm, a 2 µm distance between the core and sensing surface, and its roughness of RMS = 40 nm. As a proof-of-concept, we have developed a lossy-mode resonant sensor with a 320 nm ITO layer and demonstrated its sensitivity of 550 nm/RIE.