Bongiorno, Meme. If you look into Erno Zwaan's book, Animal Magnetism, half of it is devoted to bass building. He uses a 2 piece body, each with one side cut at about an 80 degree angle and then glued together where the angled sides of each piece meets. This gives about a 20 degree angle to help make the curve. Then he does his shaping. However, as a newbie, Zwaan recommend that you start with a one piece, or glued up flat piece say 2 inches or 51mm thick and carve it out as the others have suggested. Vincenzo e Garhanmann's idea is great. It's harder to do your routing with the pre-angled piece. Caio! - Tomaso
After writing this, I have a strange yearning for some espresso (NOT eXpresso) and biscotti (pronounced bis coat ie!)!