The Slab is a flat "cut-out" shape. Like the Blob you draw a Loop taking care not to intersect itself.
4.1. The Guitar
Choose the Create Slab Tool and draw the shape below in the front view - taking care to stay one side of the centre line.
Next turn on Symmetry
in the Object Properties.
If you want to move or rotate a Symmetrical slab you must first 'bake' the curve driven object into a simple mesh. Just press 'K' to convert.
While this means you lose access to the control curve, you can now freely move and distort the object.