Prepare the pan-sagna. In a large sauté pan, heat some olive oil over high heat. Add onion and garlic and cook until translucent. Season with salt, pepper, red pepper flakes and oregano. Add crushed tomatoes and chicken stock. Bring to a boil. Add chicken and broken up lasagna noodles. Stir to incorporate. Sprinkle cheese over top and cover with foil or a lid. Simmer on low for about 20-25 minutes.