The full formal proposition: a boned sweetheart bodice coming to a point at the front waist, a skirt with enough fullness to move properly, and a train. This is the most demanding garment on the site to make, and the one where having it made rather than bought changes the result most.
What it asks of the maker
A strapless bodice has to stay up without being tight, which means boning at the seams and an internal waist stay carrying the weight of the skirt rather than your ribs doing it. That is skilled work. Expect two or three fittings and budget at the top of the estimate.
Notes for your dressmaker
Satin shows every needle mark permanently, so mistakes are not recoverable — ask for a toile in cheap cloth first. The hem will need horsehair braid or a petticoat to hold its shape. And ask for a bustle loop so the train can be lifted after the ceremony.