thi is called Wedging, its a dull tedious and labour intensive undertaking.
if the clay is too wet, you have to knead the clay onto an absorbant surface to work out the excess water. This project builds a table for this purpose. a wood fram surrounding a 3 inch thick hard plaster top. with a convient clay storage shelf under neath.
Step 1: Building the top frames
you need three of these.