I am having serious problems with the chuck pot roast which is supposed to just fall apart in the crock pot. I make my own salsa, so 1st, I sear both sides of the roast for about 2 minutes,when I put the roast in the crockpot with seasonings and the salsa, I put it on low. After about 4 hours, I flip it over. Add more salsa, I like it hot. 4 hours later I pull it out, and end up cutting the meat with a knife. What am I doing wrong??