I dry cooked chicken but have not tried pork. I don't think you'd get crackling but you could finish it off in a hot oven for half an hour. That might work.
I have just checked my instruction book and mine must have liquid in it otherwise the pot will crack, maybe explosively...so it might be worth checking your manual, you don't want to lose your lunch.
I don't put in any liquid when I do my chicken. It creates its own liquid. I do stand it on a few sliced carrots, though, in case it sticks to the bottom.
I don't put liquod in mine, as soon as I switch it on the bloody condensation starts. What I do do is scrunch up balls of tin foil to put the joint on so it doesn't boil in the bottom of the pot.
Add no liquid the meat will cook in it's own juice's. You will not get crackling so take that off first and put it under the grill to cook and crisp it.
Do you realize that you do not even need to defrost first to slow cook?
Just add an hour or three to the cooking time and bung it in frozen.
May have had a surprise in your case though!