Lean pork loin cooks quickly, which is a disadvantage in a slow cooker. Cook's Country has discovered how to make it work. Wrap the seasoned pork in foil, invert a loaf pan to elevate the pork above the bubbling juices, where it can cook gently, and put the apple-onion mixture on the bottom to make a tasty compote to serve with the pork. A pork loin roast about 9 inches long will fit best. Nestle the inverted loaf pan into the apple mixture so that the pork fits on top and the cooker can close.