Season the pork well with salt and pepper, set aside.
Layer the bottom of the crock pot with the onions, carrots and garlic.
Place the pork on top of the vegetables and then surround it with the apple quarters.
Top the pork with the rosemary, cover with lid and cook for 6-8 hours on low. It really depends how hot your cooker is, mine is pretty hot so it usually only needs the 6 hours. You could always check the meat and ensure a meat thermometer reads 160F degrees.
Remove the pork and slice for service. Spoon out the carrots and onions to serve with the meat.
Remove the rosemary springs and larger pieces of garlic and discard.
With the remaining liquid you can make a gravy by adding a corn starch slurry** or flour to thicken the liquid, whisking well to avoid clumps and to desired thickness.