I used a block to split this pile of black locust today. Look carefully and see it barely visible among the splits on the ground. The locust came right off the PU and the largest round was maybe 12".
If I'm using an axe, and they're s.aller rounds I will put them on a chopping block to keep the axe head out of the dirt
For a block I find a big round 30” or so that’s about 3-4” just thick enough so it doesn’t split. 1. so axe/maul doesn’t hit ground and 2. It’s harder than the ground. I split big rounds in the ground so I don’t have to move them. I also like splitting right in the stump when possible.