Hi elle5,
I don’t have any personal experience with the FossFlakes pillow so I can’t make any meaningful comments about it and you are the first one to mention them on the forum but hopefully some of the forum members that have purchased it will see your post and share their comments and feedback.
They are made from polyethylene which is a type of plastic that can be used to make fibers for filling or stuffing and for food grade products such as bottles as well. They are Oeko-Tex certified so they would certainly be a “safe” material.
As you probably know a suitable pillow is an essential part of good alignment for the head and neck and upper body because the gap between the head and the mattress and the curve of the cervical spine needs to be supported just like all other parts of the spine. Like mattresses … there are certain “needs” that depend on body type and sleeping positions but with pillows more than mattresses, personal preferences play a more important role because the face is much more sensitive to textures, temperature, smells, and other more subjective “feel” based properties of a pillow. There is more about choosing pillows in the pillow thread here including a number of links to some additional forum posts and topics that discuss various pillows as well in post #3 in the topic.
There are also some pillows that use Kapok mixed with shredded latex such as here and here that would help the Kapok maintain its loft and resiliency.
Phoenix