"His uncle always pours a lot of salt onto the meat."
Translation:Lia onklo ĉiam ŝutas multe da salo sur la viandon.
I forget which duolingo unit has this information in its Notes, but this is the "accusative of direction". https://books.google.com/books?id=93EZAAAAYAAJ&pg=PA37&lpg=PA37&dq=accusative+of+direction+esperanto&source=bl&ots=wwqLdiUAFL&sig=byDGEEPmb9Wtu6NoKMtOUgdKdzU&hl=en&sa=X&ei=dyVzVczBMPWasQS_w4AI&ved=0CD8Q6AEwBQ#v=onepage&q=accusative%20of%20direction%20esperanto&f=false
"sia" refers back to the same person, usually the subject of the sentence. If Jack likes Bob's uncle as well as his own uncle, it's "Jack sxatas lian onklon kaj sian onklon." If you want to then refer to Jack's uncle, you could use "sia": "Jack sxatas lian onklon kaj sian onklon. Sia onklo estas afabla ulo." However in the given stand-alone sentence, "his" doesn't refer back to anyone discussed previously.