Flip the t-shirt inside-out.
Sew the neck hole and arm holes closed, sewing the fronts to the backs. If you're using stuffing rather than a pillow form, sew along the bottom of the t-shirt to close the front and back together leaving an opening about 4 inches wide.
Turn the shirt right-side out.
Stuff polyester stuffing into the arm holes and lightly fill the neck and shoulder area.
Continue stuffing the shirt with polyester stuffing or use a pillow form to fill out the rest of the t-shirt.
Use the needle and thread to stitch the bottom of the t-shirt pillow closed.