Add the cubed butternut squash, white beans, diced onion, minced garlic, and chopped sage to the slow cooker.
Pour the vegetable broth over the ingredients and sprinkle in the salt and pepper.
Stir everything until the ingredients are evenly distributed.
Cover the slow cooker and cook on low for 7 hours, until the squash is very tender.
Use a potato masher to press down on some of the squash and beans a few times for a thicker texture.
Stir the stew once more and serve hot.