Mix your coarse salt with the rosemary and thyme in a small container and give it a good shake, setting it aside. You can do this beforehand and just keep it around until you need it.
Unwrap the tube of polenta and cut in half, crosswise. Slice each half into three slices lengthwise and then into thick cut, fry-size pieces. Don’t overthink it—in the end you want them to look like thick cut French fries.
Drizzle some olive oil on a rimmed baking sheet lined with parchment or spray with your olive oil cooking spray. Arrange your “fries” in a single layer and brush with more olive oil or spray them with more olive oil cooking spray and season with about half of your herbed salt. Throw them in the oven on the centre rack and bake for about 30 minutes before flipping them with a spatula and then bake for another 8-10 minutes.
Remove from the oven and let cool a couple of minutes before removing them and throwing them on a plate to serve with the Truffle Mayo.