The Constellation-X mission is a follow-on to the current Chandra and XMM missions. It will place in orbit an array of four identical X-ray telescopes that will work in unison, having a substantial increase in effective area, energy resolution, and energy bandpass over current missions. To accomplish these ambitious increases new optics technologies must be exploited. The primary instrument for the mission is the Spectroscopy X-Ray Telescope (SXT), which covers the 0.2 to 10 keV band with a combination of two x-ray detectors: a reflection grating spectrometer (RGS) with CCD readout, and
a micro-calorimeter. Mission requirements are an effective area of 15,000 cm2 near 1.25 keV, 6,000 cm2 near 6 keV, and a 15 arcsec (HPD) resolution requirement with a goal of 5 arcsec. The Constellation-X SXT uses a segmented design with lightweight replicated optics. A technology development program is being pursued with the intent of demonstrating technical readiness prior to the program new start. Key elements of the program include the replication of the optical elements, assembly and alignment of the optics into a complete mirror assembly and demonstration of production techniques needed for fabrication of multiple units. In this paper we present the development of SXT assembly and alignment techniques and describe recent work and current status on the first of these assemblies, the Optical Assembly Pathfinder, in which precision mechanical techniques and optical metrology are used to assemble and align the flexible optical elements.