Cut each apple in half then scoop out and discard the seeds and stems. Cut each half into 4 slices so that you have 8 slices per apple. Place the apple slices in the slow cooker.
Add the whole cloves, cinnamon sticks, and water.
Cover and cook on high for 4 hours, until the apples are soft and mushy in texture.
Remove the lid and carefully take out the cinnamon sticks.
Using an immersion blender, blend the apples until the cider is smooth.
Return the cinnamon sticks to the slow cooker.
Replace the lid and continue cooking for an additional 2 hours.
Add the brown sugar and stir until dissolved.
Remove cinnamon sticks then, over a large pot, ladle the apple mixture through a fine-mesh strainer, pressing down on the apple pulp with the back of the ladle to extract the liquid.
Taste and add additional brown sugar, as needed, to taste.
Serve hot or allow to cool then refrigerate to serve cold later.