Wash, peel, and take out the seeds from the apples. Slice thinly. Measure out four quarts of apples. Pour all apples into slow cooker.
4 qt apples
Add brown sugar, cinnamon, cloves, anise pod, salt, and lemon juice. Stir to incorporate everything.
2 ¾ cups light brown sugar, 2 ¾ tsp ground cinnamon, ¼ tsp ground cloves, 1 star anise pod (optional), ¼ tsp kosher salt, 1 tbsp fresh lemon juice
Turn slow cooker on high for 4-5 hours. After the first hour, remove the star anise pod, if added. Every hour, stir the apples.
Once the mixture is bubbling and cooking well (after approximately 4-5 hours), turn the slow cooker to low and leave for 10-12 hours. I usually do this in the evening so it can sit on the low setting overnight.
After ten hours, start checking the slow cooker. Stir mixture using a strong wire whisk or hand potato masher to break up the apples.
Once the butter is the consistency desired, use a blender, food processor, or immersion blender to break down the rest of the apples to achieve an even consistency.
Remember that apples contain a large amount of water and will cook down considerably. They also vary a lot in how they cook. My apples had a lot of liquid in them so I needed to give them 2 extra hours on high (with the lid off) to make sure my apple butter turned out as thick as I wanted.