Pour the red wine into your slow cooker.
Add the orange slices, brandy (if using), honey, cinnamon sticks, cloves, and star anise into the slow cooker.
Stir gently to combine the ingredients.
Set the slow cooker to the “Low” setting and allow the mulled wine to warm up slowly. It typically takes about 1 to 2 hours for the flavours to meld together.
Once warmed through and infused with the spices, reduce the slow cooker to the “Keep Warm” setting to maintain the ideal temperature without boiling.
Prior to serving, you can use a ladle or a fine mesh strainer to remove the spices and citrus slices from the mulled wine.
Serve the mulled wine warm in heatproof glasses or mugs.
Optionally, garnish each serving with a fresh slice of orange, a cinnamon stick, or a star anise pod.