Pinch Pot Research.
Pinch pots are a basic way of building a vessel out of clay. One starts with a sphere of clay then pushes a thumb into the sphere without going through the back. Then using the thumb and fingers in a lobster-claw like fashion, pinch the opening of the clay larger and larger until the desired size is achieved. I recommend making the thickness of the walls of the vessel about width of a finger. Make the vessel with quality.