ZHANGJIAKOU, China—Alex Hall’s final trick was called “the pretzel.” His stomach knotted up just thinking about whether to attempt it. He did—because it’s the Olympics, after all—and by putting his personal spin on the slopestyle course Wednesday, he skied away with a gold medal. The freestyler led a 1-2 American with a trick on his first run where he stopped his rotation midair and turned in the other direction before softly landing. Hall’s opening performance drew a score of 90.01, which no one could match in three runs. His teammate Nick Goepper turned in a creative run on his second pass to earn silver. Jesper Tjader of Sweden took home bronze. “I wasn’t sure if I could land it,” Hall said. “I was just kind of going for it, and going all in. It worked out. I’m so hyped.” The American men have captured six of nine Olympic medals since …