Ordinarily I use the bandsaw to cut round blanks for bowls, but large, heavy pieces I do with a small chain saw. I measure the diameter two ways making a center cross mark. Setting a large compass on the mark I draw a circle and cut it out with 8 slanting cuts. If one of the points protrudes too far I also cut it off.
After screwing on the faceplate one or two of the points sometimes will strike the bed of the lathe. Usually this means removing the blank from the lathe and using a chisel to knock off the points. Yesterday I suddenly remembered the power hand planer which I bought for a single job years ago. Dug it out and it buzzed the corners down in a jiffy, right on the lathe. Duh!! After 15 years of turning I thought of it.