Start with a slab of ice

Find the center with a layout jig

Using a layout jig & 2 ice picks, draw on a circle

Using a chainsaw, cut out the circle (stay on the outside of the scribed line)

More cuts will make a better circle (this is easier with a longer bar)

Notice the foam under the carving?  This protects your saw

Using a pistol grip sander, sand the entire surface

Using a used piece of sand paper break over the corners