During the first hub of the game, look past the swing and behind the house. You will find a deer skull. This is the 1st collectible.
When you go into the main building to visit Louis and AJ, walk behind the stairs. On the right side, you will find fake flowers.
When helping AJ make friends and waiting for dinner, go to the side of the hub. At the end of the walkway, you will find the real flowers.
When Violet comes to tell you about Sophie and Minerva, she will pressure you into giving Tenn the box of supplies. To get this collectible, you can either let AJ keep the box or return it to Violet, as she will let AJ finish before bringing it back to Clem.
For this option you must go fishing with Violet and Brody. Do not go hunting with Louis and Aasim. When you are indoors, look at the top of the mantle to find the cat skull.
When talking to Tenn in the school yard, let him draw you into his picture.
Now, to use your collectibles
Now, in the beginning of act 3, go around your room and place all 6 of your collectibles!