If you don't specify when ordering, the standard is this:
- On guitars and basses with a 5-piece neck, and a flamed, quilted or figured top, the neck will show
- On guitars and basses with a one or two-piece neck (koa, mahogany, walnut), and a flamed, quilted or figured top, the neck will not show
However, you can order whatever configuration you like - for example, you can order a 5-piece neck that doesn't show, or a 1-piece neck that does, so long as you order a flamed, quilted or figured top. It's important that you are clear with your salesperson on whether or not you want your neck to show, otherwise, you will get the standard described above.
Note that on Icon basses, the default is for the neck to show through, regardless of what kind of top or neck the instrument has. If you don't want this, be sure to specify "NS" when you order.

LB70 with no-show flamed koa top (NS)

LB76A with flamed maple top, 5-piece maple/koa neck, and neck showing through (not NS)