Laurel are stately plants, that do make fine bushes. They are evergreen too, so provide much better screening than hawthorn or privet.
How far apart to plant them, and how close to the fence, depends how wide the gap is, how deep the border is, and how big you'd like the plants to grow.
You could place them equally spaced in the gap. I would think that you need to leave at least 30cm between them and the fence. But it depends on how big (or small) you want to keep them.
The shade cast by laurel is quite dense. So other plants may struggle to grow beneath them. One benefit of that is that they also supress the growth of any weeds.