Prepare a skillet with a small amount of oil over medium-high heat. Season the roast with salt and freshly ground black pepper then place into the skillet and brown each side for about a minute; 4 minutes total, to help seal in moisture and give it a nice color. Set aside on a plate to cool slightly.
Finely dice the chipotle pepper and chop the cranberries if desired.
In a small bowl combine the syrup, diced chipotle, freshly grated ginger, salt and pepper. Rub the mixture onto the roast then place it and any remaining rub into the bottom of a slow cooker. Add the cranberries and pour the chicken broth down the side of the pan (avoiding rinsing the rub from the roast).
Cover and cook on low 8 to 10 hours.
Remove roast and set on a serving platter covered with a tent of aluminum foil; reserving liquid. Keep slow cooker on low and add water and 1/4 tsp guar gum, xanthan gum or Thick-It-Up thickener to the reserved mixture, whisking to combine. Continue to cook on low heat until the sauce thickens slightly. Once thick enrich the sauce if desired with 1 tbsp unsalted butter, adding additional salt and pepper - to taste. Serve the sauce over the pork roast. You should have about 1 cup of sauce, each serving is 2 tbsp.
Tip: It is not necessary to chop the cranberries for this recipe (they will break down while cooking), chopping them makes the sauce smoother.