If you don't have time to thaw them ahead of time, you can throw them in the crockpot frozen, just be sure to cook them a little longer--5-7 hours instead of 4-6.
Instant Pot recipe update: Defrost this freezer meal in the fridge then place in Instant Pot for 25 minutes on high. Once time is over do a quick release and then remove the majority of the liquid then place IP on sauté for 4 minutes. Ribs are full of flavor and so tender.