Chapter 3 - Begins at 13:05
in the video below.
Right at the start, there are a bunch of eyes with lights above them to the right. Just strafe left/right starting with the right-most one to activate each one at a time so the lights are above all 5. Following this, you'll have 5 eyes on pedestals in the next room with roman numerals I-V at their base. Look at your feet when not activating them, and activate them in order I, II, III, IV, V to open the next door.
Next back up into the corner to the left of the door when you enter to see the four 'clocks' with eyes on them on the upper level. With all four in view, run straight forward into the middle and look at the 5th to open the door.
With the glowing puzzle on the floor, look at the eye to move it, and look up at the ceiling/down at the floor when you reach a wall you can't pass to move on in the inverse version of the puzzle. Get the eye-block to the far side to complete it.
Following this, you'll have a RNG puzzle with red lights on the opposite side. Push the buttons matching the far side's lights and keep the far side in view as you cross the water. If you look away it will reset. Do the same on the far side to drain the water.
Down below you'll have a wall with four rows of 3 squares in it. This is the puzzle for another secret achievement. The squares will 'fill' when you move toward it and 'empty' when you move away. Position your camera so only the squares you want to affect are in view, and move forward/back to fill or empty them in order to get all 12 'full'. This opens the door behind you. Head outside and keep the black planet in view, rotating it up to block the sun. You'll unlock Body.
Down the hall you'll see a hexagonal colored puzzle. You need to get all adjacent sides to be the same colors. Rotate the center portion to get the triangles positioned correctly then rotate each triangle as necessary to match up the colored sides. I'm not sure if this one has RNG in it so check the video for Chapter 3 to see this one in action. You should have a Red/Dark Blue/Yellow triangle by the red side, a Dark Blue/Dark Blue/Red triangle by the blue side, and a Blue/Green/Red triangle by the green side. This should set you up for the solution. Head back upstairs and exit to the dais to finish and unlock A Crafted World.