It's made of three panels of sheer cotton, whip stitched together at the selvedge. I made slits on both sides, folded and pleated the top edges and whip stitched them on long tapes, front and back separately. It is worn over hand sewn linen petticoat and a false rump.
It is hand sewn, linen with linen tread, filled with unprocessed cotton fiber.
I based it on this drawing from Manchester Art Gallery: