Place peeled, cored, and sliced apples into the slow cooker.
Add sugar, cinnamon, cloves, lemon juice, salt, and star anise (if using). Stir to combine.
Set the slow cooker to high and cook for 4-5 hours, stirring occasionally.
After the first hour, remove the star anise.
Once bubbling, switch to low and cook for 10-12 hours (overnight works great).
Use a whisk or potato masher to break up the apples.
Turn the cooker to high, remove the lid, and cook off excess liquid until thickened.
Blend with an immersion blender for a smooth texture. Cool, then freeze or can for later use.