I split mine with a brickies bolster chisel, the I had a reasonably flat surface to work on. The tree seems to grow to the right diameter for a bowl and the pith is central to the bowl. the wood is hard and oily and take a great shine. I got mine by being between the bowls and a skip!
We had some brought to the club for reuse, but were the modern Bakelite one's, One member tried to turn one and every one else headed for a handy skip!
Ron