Ooooh. I did follow the shadows after aligning them, but because i did not think of interacting with an invisible target, I just carried on walking until I clipped out and fell forever. I understand that having a prompt show up for the invisible teleporter would give it away and ruin the puzzle, so maybe just add an invisible wall around the island? And specify that the teleporter is invisible (I was expecting some kind of portal).
I will give it another go now! Thank you!