Peel and quarter 1–2 onions and place them in the bottom of the slow cooker to form a bed for the chicken.
In a small bowl, combine 2 teaspoons salt, 1 teaspoon paprika, 1/2 teaspoon onion powder, 1/2 teaspoon dried thyme, 1/2 teaspoon black pepper, and 1/2 teaspoon garlic powder.
Remove the chicken from packaging and discard the neck and giblets if present. Pat the chicken dry with paper towels.
Rub 1 tablespoon olive oil all over the outside of the chicken, then sprinkle the seasoning mixture evenly over the chicken and rub it in to coat.
Place the seasoned chicken on top of the onions in the slow cooker. Cover and cook on low for about 4 hours, or until a meat thermometer inserted into the thickest part of the thigh registers 165°F (74°C).
Optional: For crisp skin, transfer the cooked chicken to a baking sheet and bake in a preheated 425°F (220°C) oven for 15–20 minutes, or until the skin is lightly browned and crisp.
