Mince the 5 garlic cloves finely to release their oils and ensure even distribution throughout the cooking liquid. In a bowl, whisk together the chicken broth, lemon juice, olive oil, oregano, thyme, salt, and pepper until well combined. I prefer using freshly stripped thyme leaves rather than dried—the aroma is noticeably brighter and more authentic to Greek flavors. This marinade base can be prepared while you're handling the other ingredients, making the next steps quick.

Slice the large onion into 1-inch thick slices and arrange them in the bottom of your slow cooker to create a bed. This layer serves two purposes: it elevates the chicken slightly so it cooks more evenly, and it prevents the meat from sticking to the bottom. Place the 2.5 lb chicken breasts on top of the onion bed in a single layer, nestling them together snugly so they cook uniformly.

Pour the marinade mixture from Step 1 evenly over the chicken, making sure the liquid reaches around the chicken and seeps between the pieces. Tuck the 2 bay leaves into the liquid for subtle depth of flavor. Cover the slow cooker and cook on low for 5-6 hours, or on high for 3-4 hours, until the internal temperature of the thickest part of the chicken reaches 165°F when checked with a meat thermometer. I like to check at the 5-hour mark on low to avoid overcooking—slow cookers vary in temperature, and overcooked chicken becomes stringy.

Once the chicken is fully cooked and tender, carefully transfer it to a cutting board or shallow bowl. Using two forks, shred the chicken into bite-sized pieces, discarding any large pieces of bone if present. Pour the cooking liquid from the slow cooker over the shredded chicken to keep it moist and flavorful. Discard the bay leaves and onion slices if desired, or leave them in for added texture and flavor. Serve warm with your choice of sides—this pairs beautifully with rice, roasted vegetables, or a fresh Greek salad.