Prepare the slow cooker: Lightly coat your 5-quart (or larger) slow cooker with nonstick spray.
Brown the chicken: Heat olive oil in a large skillet over medium-high heat. Season the chicken with salt and pepper, then place it in the skillet, seasoned side down. Let it brown for 1-2 minutes on the first side, then flip and brown for another minute on the other side. If your skillet is too small, brown the chicken in batches to avoid overcrowding.
Transfer to the slow cooker: Once browned, place the chicken in the slow cooker.
Add the vegetables: Arrange the roasted red peppers, olives, and onions around the chicken, avoiding placing them directly on top.
Make the sauce: In a small bowl or measuring cup, whisk together the lemon juice, minced garlic, honey, oregano, and thyme. Pour this mixture over the chicken and vegetables.
Cook: Cover and cook on high for 1.5 to 2 hours or on low for 3 to 4 hours, until the chicken reaches an internal temperature of 165°F and is fully cooked through.
Serve: Serve the chicken warm, topped with crumbled feta cheese and fresh herbs of your choice.