Core the pear and apple, then slice both into 1/2-inch thick wedges. Slice the orange into 1/4-inch rounds. Set the orange slices aside separately from the other fruit, as they'll be added later. Having your fruit prepped and ready ensures the slow cooker can start working on building flavor immediately without interruption.

Pour the red wine, pomegranate juice, brandy, and triple sec into your slow cooker. Add the sugar substitute and stir well to ensure it's fully dissolved. This liquid foundation will infuse with the spices and fruit over the next couple of hours, developing deep, complex flavors.

Add the cinnamon sticks, whole cloves, and star anise to the sangria base, stirring to distribute them evenly. Then add the pear and apple wedges, pushing them gently into the liquid. I like to add the citrus spices early so they have time to soften and release their essential oils into the sangria, creating a warming, aromatic depth that can't be rushed.

Cover the slow cooker and cook on low for 2 hours. This gentle, extended heat allows the spices to fully infuse into the liquid, the sugar to caramelize subtly with the fruit juices, and all the flavors to meld together harmoniously. The fruit will soften slightly while still maintaining its structure.

After 2 hours, stir the sangria gently and add the reserved orange slices. I add the oranges at the end because their bright, fresh citrus flavor is best enjoyed fresh rather than stewed—they'll soften slightly in the warm sangria but maintain more of their character. Ladle into glasses with some of the fruit and spices, and serve warm or at room temperature depending on your preference.