Here’s a little tip to help curvy women with a boudoir pose to hide her belly. I sometimes use stiff organza fabric, partly to style an image but also to (subtly) conceal areas of the body that my client would prefer to hide. Typically I find this tends to be her tummy area. I use a stiff organza which not only adds a bit of softness and interesting texture for the lighting but it also stays in place.
Always communicate with you client to let her know if you need to adjust anything near her body and… male photographers ask your female assistant or makeup artist to do this for you, its so important to keep your client comfortable and feeling safe.
You can see here how the organza fabric is used to hide her tummy (and for modesty). So she can still look beautiful, confidently nude in her natural body shape.