My aim with this video was to be as thorough as possible, so I try to show off as many landmarks as I can in order to help you get your bearings and understand the orientation of the map a little easier.
The flower is hidden in a little valley between sand dunes, amongst some rocks. It's a reference and homage to thatgamecompany's previous title, "Flower".
After finding the second cloth and symbol 7, turn towards the mountain and climb over the sand dune. You should see some small rocks dotted around in a row on the floor ahead. Follow them. You'll come to a valley between sand dunes and should see the flower amongst some stones. Stand next to it for a while and eventually the "Mirage" trophy will pop.