On February 23, 2006, about 0910 Pacific standard time, a Cessna 150L, N11568, registered to and operated by Twin Oaks Airpark, as a 14 CFR Part 91 instructional flight, experienced a loss of engine power while maneuvering near Hillsboro, Oregon. During the emergency off airport landing, the aircraft nosed over during the landing roll. Visual meteorological conditions prevailed at the time and no flight plan was filed. The aircraft was substantially damaged and the student pilot, the sole occupant, was not injured. The flight originated from Hillsboro, about 30 minutes prior to the accident. During a telephone interview and subsequent written statement, the student pilot reported that he was practicing maneuvers in the practice area. The student stated that before returning to the airport, he decided to practice a power-off stall. The student climbed to 3,000 feet and leveled off before extending the flaps to full and slowing to 50 mph. The student then pulled on the carburetor heat and throttled back to idle. The student stated that before he pulled up into the stall and before feeling the buffeting, the engine lost power and the propeller stopped. The student turned toward the airport and issued a mayday call to air traffic. The student pilot did not think that he could make a successful landing at the airport and turned toward an open field to initiate an off airport forced landing. During the landing roll on soft terrain, the aircraft nosed over. At the time of the accident, the nearest weather reporting facility located at the Portland-Hillsboro Airport was reporting at 0853 a temperature of 44 degrees F. and a dew point of 40 degrees F. The probable carburetor icing chart indicated that for the existing temperature and dew point, the aircraft was operating in the serious icing in cruise or climb power range. The aircraft was recovered from the accident site and taken back to the owner's facility. On February 28, 2006, in the presence of a Federal Aviation Administration Inspector from the Portland-Hillsboro, Flight Standards District Office; the engine was prepared for an engine run. The engine started without difficulty and was run at varying power settings with no anomalies noted for several minutes before it was shut down.