Klim Kostin (St. Louis Blues) and Nikita Shashkov scored, and Pyotr Kochetkov made 16 of his 34 saves in the third period for Russia, which finished fifth at the 2018 WJC in Buffalo, the first time in eight years it failed to win a medal.
"It's truly a big day, a long time working towards this," said Kochetkov, who wasn't picked in the 2018 NHL Draft. "Thank you so much for the team, thank you for [the] coaching staff, that they believed in me and gave me the chance."
Valentin Nussbaumer and Yannick Bruschweiler scored, and Luca Hollenstein made 19 saves for Switzerland, which was trying to win a medal for the second time at the under-20 tournament.
"We had enough chances to win the game but I don't have a medal around my neck," Switzerland coach Christian Wohlwend said. "But proud about the whole tournament, absolutely."
Slepets made it 1-0 at 4:25 of the first period, skating unchecked off the boards and shooting between Hollenstein's legs. Slepets beat him five-hole again with a breakaway deke at 6:33 of the third period and completed the hat trick into an empty net with 2:01 left.
Slepets (5-foot-10, 165 pounds), a C rated skated on NHL Central Scouting's Players to Watch list for the 2019 NHL Draft, had seven points (five goals, two assists) in seven tournament games.
"I was not so good during the whole tournament but this game I was able to score three goals and that helped the team," he said. "The main thing for me is to help the team get the win."
Shashkov made it 2-0 at 13:44 of the first period, but Nussbaumer scored off a move at the top of the crease to make it 2-1 at 4:54 of the second.
Kostin scored on a 3-on-1 to make it 3-1 at 12:53 of the second period.
Bruschweiler made it 3-2 with 4:24 left in the second period, batting a puck out of the air after Kochetkov was stranded making a sprawling save at the side of the net.
"The first period was terrible and I couldn't understand. We had a second chance to win a medal for our team and how we played," Wohlwend said. "I don't know what the players were thinking. Then I got louder in the dressing room. I had to wake them up, kind of, and it worked. All the chances we created against Russia was crazy for us but we couldn't bury our chances and that's why we lost."
