Put the beans, water, crushed red pepper, salt, and black pepper into the slow cooker and stir. Cover and cook on low until the beans are tender but not falling apart (7 to 9 hours). The time will vary depending on the size and age of the beans. Once cooked, turn off the slow cooker. If you leave the beans in the slow cooker for a while, they will continue to absorb the liquid as they cool, making them more tender and creamy.