Dividing Bay Tree

I just bought my first bay tree! It is about 12" tall and in its second year with good leaf growth up the stem. There are also two stems in the pot, one on each side of the "main" stem. These are about 8" tall with good leafing. The nursery said it was time to repot it, and I did. My question is can those stems be separated to form 3 trees. I could not see where these other two stems join the root ball is it did not become totally uncovered in the repotting.

You will have to dig down to the roots to see if the sideshoots have any roots on them. If they have many, just unpot the whole plant again, cut through the connection to the rest of the plant with a sharp knife and tease the roots apart before replanting in separate pots.
If there seem to be no roots or just a root or two I would wait until next spring before checking again. You could also try at the joint to the main stem, cutting the shoot off only halfway through the connection, dusting the cut with lots of sulphur and maybe some rooting hormone and waiting at least half a year before checking the state of the roots again. By doing it to one shoot only, you still have the other one to try other things with.
The other thing to do, could be to scrape off a strip of bark on the underground portion, dusting it with sulphur and rooting hormone and recovering it with sterile soil. Again wait half a year before disturbing anything again.