Pat the whole chicken dry and season it evenly with olive oil, salt, pepper, paprika, garlic powder, onion powder, thyme, and rosemary so the flavor coats every part of the chicken properly.
Layer onions, carrots, celery, and garlic in the bottom of the crockpot to create a natural rack that helps the chicken cook evenly without sitting directly in liquid.
Place the seasoned chicken breast-side up on top of the vegetables, add broth if desired, then cover tightly with the lid before slow cooking.
Cook on LOW for 6–7 hours or HIGH for 4–5 hours until the thickest part of the thigh reaches 165°F and the meat becomes tender and juicy.
Let the chicken rest for 10 minutes after cooking so the juices redistribute through the meat before carving and serving.
For crispier skin, broil the cooked chicken for a few minutes in the oven until golden brown before slicing and serving.