You can slather gravy all over mashed cauliflower and whatever meat created the gravy. The initial question was about thickening stews too.

Two of my favorite techniques for thickening are using well cooked and pureed cauliflower, or cream cheese or a combination of both. Just add a little at a time until you get the right consistency.
Yes, it's the quality of the carbohydrates. That, and some peoples bottom line with low-carbing does not include refined grains or sugar. Any amount can set them off and they've learned by experience.

Karen