In the third trimester, the best use of a Flatter:Me is to give a round belly an even rounder shape. You know how some of those maternity sweaters or dresses fit... but they make you feel even BIGGER than you currently are? Just use a Flatter:Me to turn a tunic (the one in this photo isn't even a maternity dress) into an empire waist dress. Looking at my photos from the front without a belt, I feel like I could have just gained a lot of weight - however, by adding a Flatter:Me, I'm definitely just very pregnant.
As an added bonus, you can wear non-maternity clothes post-pregnancy too. The belt will just go around my waist when I get a waist back. I do miss my waist!
These photos demonstrate how to wear Flatter:Me in the 3rd trimester. Snug up those tent dresses!