Add the diced apples to a 1 to 2-quart slow cooker. Sprinkle spices evenly over the apples.
Pour the maple syrup and molasses on top of the apples, stir to combine. Cover and cook on low for 5–6 hours, until apples are tender.
Turn off the slow cooker, remove the lid, and allow the apples to cool for a few minutes. Using an immersion blender, puree the apples (directly in the slow cooker) until smooth. Alternatively, you can transfer the apples to a blender to puree them. If you do the latter option, take care as the apples will be hot. Return the apples to the slow cooker after blending. Turn the slow cooker back on low and cook, uncovered, for another 1 to 2 hours until thick and caramelized. If your mixture still appears runny, continue cooking until your desired consistency.
Turn off the slow cooker and let the apple butter cool for 30 minutes. Transfer to an airtight container and store in the refrigerator for up to three weeks. You can freeze the apple butter in an airtight container (leave about 1/2 inch of room at the top) for up to 3 months. To defrost, remove from the freezer and allow to thaw in the refrigerator overnight.