Season the chicken thighs with salt/pepper. Heat 2 tbsp of oil in a skillet over medium-high heat. Cook the chicken thighs until browned, then remove from the heat and transfer to crock-pot.
Heat 1 tbsp of olive oil in a pan. Stir in the onion, and garlic cloves. Cook until fragrant. Remove from the heat and transfer to crock-pot.
Add the remaining ingredients. Stir to combine and cook on medium-high heat for 4 hours, or on low for 7-8 hours.