Rinse pork with cool water and pat dry. Set aside.
To pork, zest both lime and orange into a small bowl. Add minced garlic, kosher salt, black pepper, olive oil and liquid smoke. Stir to combine, set aside.
Cut tested orange in half and squeeze juice into a slow cooker. Cut tested lime in half and squeeze half of the lime into the slow cooker (about 1 tablespoon). Reserve other half of lime for slaw. Place pork in slow cooker and turn to coat in citrus juice mix. Pour the citrus zest mixture onto meat and use clean hands to rub all over, coating all sides of meat. Cook on low for 6-8 hours.
About 15-20 minutes before pork is finished booking, combine all slaw ingredients, including reserved lime juice, in large bowl and toss to coat. Refrigerate until ready to use.
Shred pork with two forks and toss with juices in slow cooker. Add additional salt to taste, if needed. Serve pork on tortillas with slaw and avocado, if desired.