How do I complete the "Not a Scratch" challenge?

My team completed this tonight. We used a cheese, so up to you if you want to use it.

If you place a pike outside the heat bubble when you have frostbite debuff, then get onto it from inside the bubble. You are protected from the frost permanently and can slowly sparrow your way to the end.

Also worth noting that when a Pike is destroyed it will respawn either at the start or nearby. So be sure to check the first spawn, then Sparrow the route to pickup the Pike again along the route. You can use the Fallen teleporters in each heat bubble to teleport back a bubble.

Here is the route.