If a stone is gummed from years of oil and swarf, oven cleaner will get the majority of surface oil off, soaking will remove the deep imbedded oil from the stone.
Heat and degreaser, thrift store slow cooker work well, or just soak until they stop releasing oil, glass or plastic pasta containers, though it can take months for all the oil to release, especially hard stones like hard thick arks or other Noviculites.
Do change the degreasing solution once a week or so. I too like Simple Green, though I have used dollar store degreaser as well.
On a fine stone, mineral oil can provide a little better finish, possibly…