Place 1 7-pound boneless turkey breast on cutting board. Cover all sides of turkey breast heavily with salt and freshly cracked black pepper.
Add 1 teaspoon garlic powder, ½ teaspoon onion powder, and ¼ teaspoon dried sage to small mixing bowl. Whisk ingredients together, then sprinkle mixture evenly onto all sides of turkey breast. Rub spice blend into turkey breast as needed. Set turkey aside.
Coat bottom and all sides of Crockpot insert with neutral-flavored spray oil.
Add 2 6-ounce boxes stuffing mix and ½ cup dried cranberries to Crockpot. Gently stir to incorporate, then spread stuffing mixture out evenly across one half of Crockpot insert.
Spread 1 12-ounce bag frozen green beans evenly across other half of Crockpot insert. Alternately, add frozen green beans to Crockpot and stir green beans into stuffing mixture, then spread stuffing mixture evenly across entire insert.
Add 2 10.5-ounce cans condensed cream of chicken soup, 1 cup low-sodium chicken broth, and ½ cup full-fat sour cream to medium mixing bowl. Stir ingredients together until fully combined, then pour gravy mixture over stuffing in Crockpot. Stir to incorporate.
Place seasoned turkey breast in Crockpot on top of stuffing and green beans, with pop-up timer facing up.
Microwave ¼ cup unsalted butter in small microwave-safe bowl until melted, but not bubbling. Pour melted butter evenly over top of turkey breast.
Cover Crockpot with lid. Set Crockpot to HIGH for 3 to 4 hours, or LOW for 5 to 6 hours.
After 3 (or 5) hours, use internal probe thermometer to check internal temperature of turkey breast. Continue cooking turkey as needed until internal temperature reaches 160° Fahrenheit. Note: Do not overcook turkey. Remove turkey when 160° temperature is reached, regardless of cook time.
When turkey reaches 160° Fahrenheit internally, use tongs to carefully remove turkey from Crockpot. Set turkey aside to rest.
While turkey rests, gently stir stuffing with fork. Leave lid off Crockpot and cook stuffing and green beans on LOW 15 minutes. Stir in additional chicken broth as needed to achieve desired consistency.
After 15 minutes, slice turkey breast. Divide slices of turkey, stuffing, and green beans into preferred portion sizes and serve hot.