Read through the pattern before cutting, you might find there are instructions for trimming the appliqued blocks later (meaning the extra is included in the beginning size) if not I would cut at least 1\2" larger... I applique a lot and generally cut at least 1" larger for squaring up later -- it is easy for a block to become a bit *wonky* so enough to square up is nice to have

Your flip flops are terrific-- you're going to have a great quilt!