The score and slip is how to join pieces with the clay made into a slip. If you can make a slip with the use it.
Regular clay can be left unfired. Regular clay is normally air dried till it is bone dry. The dry clay is very brittle. It can be in the studio until you want to fire for months.
The bone dry clay is in the form that it is easiest to break.
If it does break, sometimes it can be repaired or sometimes it is broken futher to reuse. Untill it fired, dry regular clay is able to revert to workable clay.
There are air dry clays that have a binder in them that sets when the clay is dry I have heard some people like claystone
http://www.pearlpaint.com/shop_search.htm?keywords=claystone
Another place to look is http://www.dickblick.com/categories/clay...
There are other clays that should be baked in an oven. They have an additive that melts and binds.
Some people also like polymer clays.
You will need to determine if you can have pieces fired in a kiln. Are you willing to bake the piece in an oven.
If you go to the craft store or to a web site, There are clays meant to be baked in the oven. Each is different so the package directions would be a good guide
I normally work in high fire clay. I pay for membership at a studio that can fire pieces.
I have also used oil based clay and made molds.
I have also worked directly in plaster.
I read about a new clay Lumina Polymer Air Dry Clay that was listed but not availble at this time that I want to try. I will have to wait till I see it available or see it in a store.