First, it can use 1 piece of wood (one piece) which directly crushed like the picture below. This violin is made of wood which directly cut 1.
Second, can use 2 pieces of wood are pressed together into one piece. Below is a sample image two piece violin. At the center of the violin can be seen between the 2 wood patch.
In general, he said one piece violin sound better than the two piece. Judging from the price of the violin one piece also generally more expensive than two piece. One piece violin making it harder than violin two piece. But do not rule out the violins sound better than the violin two piece and one piece.