HeyDuke,
Plenty of people switch specialities during their first year. I don't think there will be too many hurdles in switching from non-clinical to clinical other than explaining why you think non-clinical was not a good fit for you.
Make sure that you spend some time with some FP docs and get some strong letters from them as well. FP does see some turnover itself so make sure
one that you know what you are getting into and two that it is something you can see yourself committed to in the long haul. I think those will be the two main obstacles you will have to explain but it is totally doable.
As far as the process, since there is turnover, there are some spots that are not always advertised for various reasons. If you know you want to be in a certain geographic location, emailing program directors with your situation and CV can get you some information about open spots. This and through word of mouth. Start by getting in touch with the FP program, if there is one, where you are training now. Since you have already started training in Pathology, I think most places would be willing to speak with you about taking you outside the match, though I am pretty sure you would still have to start as a PGY-1. Otherwise, you can always try to scramble into an open PGY-1 spot after Match Day.
If this is what you truly want, it can be done. Best of Luck. Feel free to PM me with any further questions.