Place the Butternut Squash (2 pound), Onion (1), Apple (1), Carrot (1), and Water (2 1/2 cup) in a slow cooker. Add Kosher Salt (1 teaspoon). Cover and cook on high for 4 hours or on low for 8 hours, until the squash and carrots are cooked through.
Stir in the Unsweetened Coconut Milk (1/2 cup).
Purée the soup in the slow cooker with an immersion blender until smooth. Taste and adjust seasoning accordingly.
For the garnish: Heat a medium skillet over medium-low heat. Add the Olive Oil (1 tablespoon) and bottom part of Leek (3/4 cup) and cook, stirring occasionally, until golden and crisp, about 10 minutes. Season with Sea Salt (1 pinch).
To serve, pour the soup into 6 serving bowls and garnish with the crispy leeks. Drizzle with more coconut milk if desired. Add Freshly Ground Black Pepper (to taste).