Usually I think they’re attached below the skirt, at least by about 1880. This is more of a flounce at the hem like you see in the late 1860’s and early 1870’s. This one just happens to be pleated instead of gathered. I’ll set it so the pleating is about an inch below the skirt hem.

I probably shouldn’t call this a foot pleating. I’ll call it a pleated flounce going forward since that’s more accurate.