For those with flat buns: These are on sale at Target this week and I understand they're designed by inventor of Spanx. I gave them a try and love that they don't compress my buns, but give them some lift and me some much needed shape back there.
For anyone interested, I wear a size 2/4 or 26/27 in pants and bought the Medium in these, and think it's the best fit. However, I don't need the thigh shaping.
I like shapewear for a still squishy waist area and no panty line.