Easy Slow Cooker Cheesy Potatoes

1 (2 pound) package frozen Southern-style hash brown potatoes

thawed

4 cups shredded Cheddar cheese

2 (10.75 ounce) canscondensed cream of chicken soup

1 (8 ounce) container sour cream

1 cup chopped yellow onion

1 cup milk

1 pinch seasoned salt

or to taste

1 teaspoon minced garlic

1 cup crushed cheese-flavored crackers (such as Cheez-It®)

divided