Cut two of the strapless bodice pattern piece. Place the two pieces wrong sides together.
Sew along the top and down each side of the back. Snip off corners.
Turn right sides out and iron flat.
Then all you have to do is sew the darts, and either narrowly hem the bottom or attach a skirt!
This is the strapless top in white with lace added.
Here's some Venice lace sewn over the top.
Or a slightly different method makes a reversible top.
Cut two pieces of different fabric. Sew the darts separately. Then place the two pieces right sides together and sew around the top, down one side, and across the lower edge.
Clip corners, turn inside out and press. In the picture both sides are the same, because I didn't know inspiration was going to strike :-) But this would be a cool way to make a reversible top. And it makes the lower edge so tidy.
Tuck the ends in and stitch across to close the opening. Then sew on snaps or velcro.