Flagstone rhymes with:
livingstone, steppingstone, blackstone, bloodstone, bluestone, blystone, bridgestone, brookstone, brownstone, capstone, cherrystone, cobblestone, cornerstone, coverstone, curbstone, eyestone, featherstone, finestone, firestone, folkstone, freestone, gallstone, gemstone, gladstone, goldstone, gravestone, greenstone, greystone, grindstone, hailstone, headstone, instone, johnstone, keystone, levinstone, lightstone, limestone, livingstone, lodestone, medstone, milestone, millstone, moonstone, poundstone, redstone, rhinestone, richstone, sandstone, silverstone, steppingstone, tombstone, touchstone, waterstone, weatherstone, wedgestone, whetstone, whitestone, yellowstone
Flagstone sounds like:
flextime, fluctuation, folkstone