The non-certificated pilot reported that during the initial climb after taking off, he lowered flaps and the airplane pitched up into a nose-high attitude. The pilot reduced power and attempted to land back on the runway, but the airplane exceeded its critical angle of attack, which resulted in an aerodynamic stall and loss of airplane control at an altitude too low to allow for recovery. The airplane impacted trees and terrain. The airplane sustained substantial damage to the right aileron, the left wing strut, and the fuselage. The pilot reported that there were no preimpact mechanical malfunctions or failures with the airframe or the engine that would have precluded normal operation. The pilot reported that he had recently purchased and reassembled the airplane and had performed multiple takeoffs and landings before the accident takeoff. The pilot reported that the nose-high pitch after the flap application was “higher than expected.”