I put on a shirt I don't care about, saran wrap, duct tape, pillow stuffing, cardboard (for the bottom) and a pole I use as a light stand for photography.
I needed a mannequin to make myself a gown for the vampire ball.
Wrap more tape evenly from your waist till the end of your t-shirt line, do it tight! Now make an even cut on the back part of your form to enable taking it off. Last but not least, use your tape again to get rid of the cut. Fill the form with the pillow filling or small pieces of fabric leftovers.