Slow Cooker Chicken & Brown Rice

1/2 large onion, diced
2-3 cloves garlic, minced
2 cups shredded cooked chicken
2 1/2 cups chicken stock
1 cup uncooked brown rice
2 teaspoons poultry seasoning
1/4 teaspoon crushed red pepper flakes
salt & pepper, to taste
2 cups frozen peas
freshly grated parmesan cheese

Grease the slow cooker insert (to help keep the rice from sticking).