Joining closed forms

In order to make a solid form from clay it must be composed from 2 separate forms with a hollow center so that the form doesn't explode when heated in the kiln. A ball of clay is needed first and must be rolled between your hands to make it as round as possible. Press your thumb or a similar sized object directly into the middle of the ball so it roughly represents the shape of a vase, do the same with another ball of clay. Across the top or lip of the form score into it and fill the scores with slurry, now join both forms together making sure not to close up the hole that will be left inside. Once joined you can mould the new form into the desired shape, a small hole is needed at the bottom of the form to allow air to escape when firing.