There were only three players within six shots of Flesch at the start of play Sunday - Carl Pettersson and Charles Warren were the closest at four shots back - but Flesch made it interesting for a while with three bad shots on the first two holes.
Flesch began the round by driving into a fairway bunker on the opening hole, a 404-yard par-4. He hit cleanly out but 40 yards short of the pin, and despite a perfect lie mishit his third shot. It skidded left into a greenside bunker, he hit out to 40 feet and two-putted for bogey.
There was more trouble at No. 2, another par-4. After a perfect drive down the middle of the fairway, Flesch's second shot sailed past the green into the rough 43 feet from the hole. And when he slid his chip 15 past the pin, he was unable to salvage par and dropped back to 17 under.
"It was just a sloppy bogey (at No. 1)," Flesch said. "I made a great save out of the bunker to even make bogey. It woke me up a little bit. Then I drove it right down the middle on the second hole, and when it went over the green, I was like, 'Wait a minute. This isn't how it's supposed to go today.' "
Flesch finally regained his stroke at the 203-yard par-3 third hole, hitting his drive to 4 feet and making birdie while Pettersson settled for his third straight par.
"That calmed me down quite a bit," Flesch said. "The last thing you want to do is watch that lead start coming back to the field, and that's what I was doing."
Pettersson found trouble at No. 4. Both he and Flesch drove into a fairway bunker along the right side, their balls stopping in the sand 6 inches from one another. Flesch hit out first and lofted his second shot to 9 feet and made birdie. Pettersson hooked his second shot left, it rolled down a hill to the right of the green, some 62 feet from the pin, and he two-putted for bogey from inside 15 feet.
Any chance Pettersson might still have had disappeared along with his ball at the par-5 fifth hole, statistically the easiest hole on the course. After a nice drive at the 552-yard dogleg left, Pettersson hooked a fairway wood low and left toward a giant water hazard. The ball landed in 3-foot-high weeds on a near-vertical slope, forcing Pettersson to take a penalty, and he made bogey again.
Warren, who finished a career-best second to Flesch at Reno in August, fell back quickly with two bogeys on the first three holes.
Flesch coasted to victory without a challenge, even though he made seven straight pars and bogeyed two of his last three holes over the 7,482-yard Atunyote Golf Club course, which played much more difficult because of a steady wind and firmer greens than the first three rounds.