Solar Ash

There is a tunnel/well in Mirrorsea (that you need to find in order to progress the main game) that flips your gravity when you jump through it. If you manage to position yourself in the dead center you can start looping up and down and get the 10 seconds easely. The achievement will pop when you land again.

First and foremost, I did not remember where this was. I found it again by accident because the other guy tells you nothing about where it is. The well is located between the 2 areas on the large cloud spire on the back right side of the pavilion/temple building (where you fight the area boss). After you glide up the spire you're looking for the side that you can see the ship from in the background. Right behind the checkpoint beacon there is a pink fungus in the acid pool. Hit it on the right side to make a rail left. It will lead you to another fungus, hit that one and the well is inside the cave that rail takes you to.

Here's a video of me popping the achievement. As other's have mentioned this is located up the cloud spire in Mirrorsea: