I don’t know if rye flour is “best,” but I was finally successful at creating a starter when I used rye. I use this one: https://www.amazon.com/Great-River-Organic-Milling-Specialty/dp/B07B45V9NK/ref=sr_1_8?crid=1QO3R5CZGEFNX&keywords=Rye%2Bflour&qid=1677372317&s=grocery&sprefix=rye%2Bflour%2Cgrocery%2C181&sr=1-8&th=1