Cut the pork tenderloin in half so that it fits in your crockpot, if it already fits, no need to cut it in half.
Mix all other ingredients together, and pour this sauce in the crockpot and set the pork tenderloin in the crockpot. Set on high and cook for 3 1/2 hours or on slow for 5 to 6 hours.
To make the gravy strain the remaining sauce. In a small sauce pan, melt 2 tbsp of butter and add about 1/2 cup of the sauce and the flour. Quickly whisk and after it thickens add remaining sauce and whisk and cook until sauce thickens, about 3 minutes. Serve over pork.