If you own the Blizzard Mountain DLC use the other solution. This will strictly cover the Stuntman skill portion for those that don't own the DLC.
A Stuntman skill comes from chaining any
Air skill with a
Near Miss skill within a few seconds of landing. Credit to
Stevio2175 and the others on reddit for figuring that out!
Any bump will work that gives you air. Just have another player on the other side of it and drive by them after landing.
You can also do this by yourself. An easy place to get it is at the Shipwreck
Bucket List 11. There is a bump on the way up that will give you air, then drive close to the bucket list truck for the near miss. Watch the video to see an example. I hope this helps!