During the waxing moon, take the Creepy Bait you got from the Eyeball Puzzle and go fishing. You’ll catch three different things. And to know how to line them up against their respective trees, you need to have completed the Rock Puzzle as well. Completing this puzzle will get you the pocket watch, which will get you another piece of mirror needed to finish The Forest chapter.
Video of this puzzle can be seen here: Fishing Puzzle on Youtube
Take the pocket watch to Sarah in the mirror. And then take the piece of broken mirror you get, back to the starting mirror during the Full Moon.