Slow Cooker Italian Sausage with Peppers and Onions

Ingredients

• 1 can tomato puree
• 2 cloves garlic, minced
• 2 tsp sugar
• 1 tsp dried oregano
• 1 tsp salt
• 1/2 tsp ground black pepper
• 1/4 tsp crushed red pepper flakes
• 2 lb Italian sausage
• 2 medium green bell peppers, seeded, and thinly sliced
• 1 medium yellow bell pepper, seeded and thinly sliced
• 1 large sweet onion, sliced
• minced basil