Trim excess fat from the pork loin
Season all sides with salt, pepper, garlic powder, onion powder, and paprika
Optional: sear the pork loin in a hot skillet for 2 to 3 minutes per side
Place sliced onions, garlic, or vegetables in the bottom of the crock pot
Add a small amount of liquid such as broth, water, apple juice, or barbecue sauce
Set the pork loin on top of the vegetables
Cover and cook on low for 4 to 6 hours or on high for 2 to 3 hours
Cook until the internal temperature reaches 145°F
Remove the pork loin from the crock pot and let it rest for 10 to 15 minutes
Slice against the grain and serve
Optional: thicken the cooking liquid into a sauce or gravy