Almost every time travel episode uses a different method and follows a different theory about how time travel works.
All you need to do is slingshot around the sun, which does not create a new timeline (According to Scotty and Kirk).
Or use some Chronometric particles, which may or may not create a new timeline (Depending on if the Borg actually assimilated the Earth in an alternate universe where the Enterprise didn’t intervene).
Or get sucked into a black hole, which explicitly does create a new timeline (According to New Spock).