Mix together all of the spices in a small bowl. Pat the pork with paper towels to dry. Use your hands to coat the pork tenderloin with the spice rub. Since pork tenderloin tends to be small, this may be two smaller pork tenderloins.
In the bottom of the slow cooker, stir together the chicken broth, soy sauce, balsamic vinegar, and garlic. Add the pork tenderloin. Cook on low for 3-4 hours, checking the pork to make sure it doesn't overcook. It should reach 145 degrees. Remove the pork and let it rest for 10-15 minutes, tenting it with foil so it doesn't get cold. Slice and serve.