The sFLASH-experiment has been built at the Free-Electron Laser in Hamburg (FLASH) to study the high-gain-FEL amplification of a laser seed from a high harmonic generation (HHG) source. Ideally, the HHG-seed can be amplified up to a GW-power level, improving both the shot-to-shot stability and the longitudinal coherence of the FEL-pulse. In 2010/2011 the sFLASH-components and sub-systems have been fully installed and commissioned within about 300 hours FLASH beam time dedicated to the seeding project. Procedures to achieve a full six-dimensional overlap between the seed and the electron bunch have been developed and tested. An important milestone reached in the commissioning period is the sFLASH-SASE lasing mode, which was being achieved on a regular basis. A step forward towards the next milestone - the direct seeding in the XUV-wavelength range - is the sFLASH-upgrade during the planed FLASH-shutdown in autumn 2011. In this contribution the main commissioning results and highlights of the operational experience will be discussed in detail.