These are bignay pugo stumps (Antidesma bugnius). Bignay is a fruit bearing tree native to the Philippines and is a popular material for bonsai enthusiasts.
It is also known as bugnay in Ilocos and isip-isip in Pampanga. It is a robust, easy to grow tree. It's fruits are used in making wine.
I don't know how this material will turn out or if they will even live. I potted it useing my homemade concrete trainer pots.
This will be a fun journey.