Starchy adjuncts which include flaked grains really should be mashed not just steeped. While you may get a small amount of flavor from steeping flaked rye you will not get nearly as much as compared to mashing. You will also get stuff you do not want such as starches, gums, proteins, etc which would be converted or broken down by the mashing process. Doing a mini mash is not that much more complicated than simply steeping and will get you far better results with this type of ingredient. Your choice.