Plant them like they do groundcover. Triangular spacing 18" O.C. I would stay away from the edges 12-15".

If you want to do rows, I believe the recommended spacing between rows is somewhere around 3 feet. I'm pretty sure that's the commercial recommendation, and you could get away with less space.

Did you order everbearing or june-bearing plants? If they're june-bearing, you can mow the plants after they've produced, and a matted row system would be easiest to mow over. Basically, you space the plants 18 inches apart and let the runners spread out to about 12 inches on both sides, cultivating any others into the soil. You would only be able to fit one row in your bed, but it would probably be easiest to maintain that way.

Everbearing strawberries don't need to be mowed as they produce all throughout the season instead of one big crop like june-bearers. You can just put them in rows and let them do their thing. I think one row would be best with such a small number of plants, but if you want 2, you could stagger them so there's one every 6 inches, so it looks something like this:

O

...O

O

...O

O
and so on. Unless you dig the runners up as they grow, it will just fill itself in and mess up your spacing anyway.

Hope this helps.