I have spare ribs in my freezer as well. I just started paleo 2 weeks ago and threw out all of my bbq sauce, wetrubs, and any other carb,dairy,sugar item.
What I plan on doing is seasoning them in dry rub:
Maybe try something like this:
Baby Back Ribs (Slow Cooker) - Slow Cooker Barbecue Ribs Recipe
Only thing I would add is some water/chicken broth in the bottom to keep them moist.
I have a fun and exciting journey ahead of me for cooking with different items