The 18th-century petticoat

The HÉLOÏSE skirt, with a wingspan of 4.80 m, consists of two cotton panels, joined at the sides, the upper end of which remains open on each side. This opening makes it easy to put on the skirt over your head. Once put on, the garment is tied as follows: we start by tying the links on the back panel, making a knot in the front; then the front panel adjusts like an apron, and is tied either at the back, or at the front by making a double turn around the waist. The ties are long enough to make this double turn before attaching them. If you are happy with just one turn, you are free to cut them to the length that suits you best.
The two sides of the skirt are pleated in the fashion of the 18th century. On the front, the pleats run from the central flat surface to the sides. At the back, the pleats start at the sides and converge at the center back.
To give this historical gown its full and gorgeous volume, it is better to wear it over a quilted petticoat or bum pad, which adds volume to the hips  and emphases the thinness of the waist.
A bum pad is available in the shop, here: https://atelier-serraspina.com/products/suzie-18th-century-bum-pad.

The 18th-century bodice

As for the jacket, it is a fairly fitted cotton bodice, fully lined in cotton poplin, the sleeves stop at the elbow. The jacket closes at the front with a band of invisible staples when the jacket is closed. The skirts measure 11 cm long from the waist line. The jacket was designed to be worn over an 18th century corset, but you can do without it.