Step 1

Place 1 chicken breast inside a gallon zip-top bag and pound with the flat side of a meat mallet or rolling pin to an even 1/2-inch thickness. Set aside and repeat with remaining chicken breasts. Season both sides of the chicken breasts with the salt and pepper.

Step 2

Heat the oil in a large skillet over medium heat until shimmering. Working in two batches, place the chicken in the pan and sear until browned on the bottom, about 3 minutes.

Step 3

Transfer the chicken seared-side up to a 5-quart or larger slow cooker in an even layer, overlapping slightly as needed. Scatter the garlic and sun-dried tomatoes over the chicken. Pour in the Alfredo sauce and water; gently stir to make sure the sun-dried tomatoes are submerged.

Step 4

Cover and cook on the LOW setting until the chicken is cooked through, tender, and registers an internal temperature of 165°F, about 2 hours. Uncover and stir in the spinach. Cover and cook until just wilted, about 5 minutes.

Step 5

Turn off the slow cooker and stir in the lemon juice. Serve the chicken over cooked pasta, if desired.