Crock pot meat has a tendancy to be a little slimy in texture if you don't brown it in a frying pan first. That's what gives it flavour.
I always dredge, season and brown it before I freeze it in meal size portions. I deglaze the pan with a little wine or broth, and dump that in the freezer bag as well. (Makes richer gravy too). That way, starting from frozen, it can sit in the crockpot for a few hours thawing, before the timer starts. It's safer than having thawed meat sitting at room temp for 3 or 4 hours.