Plus-size cotton panties, seamless microfiber or lace, high-waisted, in shorts or briefs, with enhanced back panels that don't roll down.
Aplus size brief is distinguished by the height of its back panel. A standard model simply enlarged keeps the same depth and rides up under the buttock as soon as you walk; a model designed for plus size lifts this panel and distributes the tension over a wider area.
It addresses two problems at once. By rising above the navel, it doesn't compress the belly at the most sensitive point, where a low rise leaves marks and rides up. And it provides enough support so that the waistband doesn't dig in. This is why the plus size high-waisted brief remains the best-selling cut in this segment, far ahead of the thong or tanga. The plus size menstrual brief follows exactly the same logic of an elevated back panel.
Three technical details make all the difference. Wide and flat elastics, or better yet, a laser cut with no hem, which doesn't concentrate the tension on just a few millimetres. A fabric containing a few percent elastane, which springs back into shape after a day of wearing. And flat side seams rather than top-stitched, in the area where thigh friction is most common.