I cook collards almost once a month and have no idea what frost has to do with them.
Take the greens and wash them off very well so there is no dirt or grit left on them. Remove the thick parts of the stems and give them a good rough chop.
I take an onion (yellow or white) chop it up and add some garlic then saute in bacon fat until tender. I add a handful of the greens and simmer until they wilt a bit then add another handful until they are wilted and repeat until all the greens are in the pot.
Simmer several hours while stirring several times adding water, broth or beer to keep them moist (they will produce their own liquid as they cook).
You can add ham, ham hocks, salt pork, pork jowls, pulled pork, and even BBQ'ed beef if you want at anytime during the simmering. It really will not affect the flavor of the greens when you add the meat.
Season with salt, black pepper, red pepper, sugar, vinegar to suit your taste.
The secret to good greens is a long slow simmering.