ITT: FTL talk
Did a cool Mantis A run where i got a mind control which I'd use on an enemy and then right before it wore off teleport them to my ship and kill them. If you have decent shielding it's probably one of the safest ways to use boarders/teleporter. You'll still want some degree of weapons of course and the flag ship was a bit tricky but it's a neat way to play.
If you're talking Rock A, get a non missile weapon ASAP and I'd recommend a teleporter. You can sell your hull plating and hull missiles for 78 scrap to help with either. Rocks have high Hp so they make good boarders. If it doesn't seem to be working by sector 3 maybe consider a retry, not getting a decent non missile early on can drag a run down.