Because you are clipping, if you look down, you can see what is below you in terms of caves. This will push the player character deeper into the composter, thus into the ground. Once you have done this successfully, look up and place the Piston directly below the Redstone Torch. It takes a moment, so wiggle around until your player character falls in. Place the Composter on the ground, touching the front of the lowest block on the same side. Place the Redstone Torch on the side of the highest block.
Stack the 4 blocks into a vertical tower.
