Some slaves/servants were highly-skilled domestic craftsmen. The widow Ellis’s housekeeper/slave Natalie, for instance, was skilled at sewing French seams in silk, while her mistress was terrified of sewing silk at all.
The French seam remains in use because it is a deft way of concealing raw edges of cloth. It is sometimes used on the outside of dresses and other garments. Natalie’s skill was one reason that the novel’s Leila Ellis hoped to employ her for wages after Emancipation took effect in Tennessee.