The fence that surrounds Baba Yaga's home is made from human bones, topped with human skulls. So it is natural that we associate bones with Her and that they are requested as offerings from time to time.
When I was visiting Iceland, I came upon this letter opener carved from reindeer bone. I was drawn to it immediately and found it nearly impossible to put down. I had not as of yet incorporated bone into my personal practice, however I had been pondering it for a while. After far too much overthinking on my part, I decided to buy it. After getting home, I realized it was for Baba Yaga. It was only after contemplating the topic of bones as offerings that I realized shells are bone and I have been using them in my practice for some time. I have a strong connection to water, so it goes without saying that shells would be a focal point for me from both a spiritual and aesthetic perspective.