How to fix a slow draining sink?
It it is a new build, then removing the trap under the sink will not be an issue.  Just loosen the nuts, remove the trap (have a pan underneath) and then clean the trap.  This is most likely the source of the slow draining.  If the trap looks clean, then get a hand auger  (snake) to clean the drain line.  It is best to do this with the trap out.  Hand augers are typically half the cost of a plumber call.  If it is still slow, then your drain vent might be clogged.  At this point, it is usually cost effective to call a plumber to clear the line.