Place chili powder, cumin, red pepper flakes, oregano, cinnamon, brown sugar and salt in the Instant Pot. Add orange juice; stir until ingredients are combined, then add onion wedges, garlic, bay leaf and pork. Stir until all pork chunks are fully coated with sauce.

Lock the lid in place, and set the Pressure Release knob to SEALING. Press the MANUAL button; program it for 35 minutes of cooking at High pressure. NOTE: If your machine has a Meat/Stew setting, you can use that also (same cooking time/pressure). It should take 13-15 minutes to reach full pressure, then the programmed cooking time will begin. *The pressure button will pop up when it's reached full pressure.

Once done, let the pressure release NATURALLY for 20 minutes. The Instant Pot will keep track of the time as the pressure is released. After 20 minutes, flip the Pressure Release knob over to VENTING. This allows any remaining steam inside to quickly release. The Instant Pot can be safely opened once the pressure button has dropped back down.

Transfer the pork pieces (using tongs) to a cutting board. Use two forks to shred the meat, then set the pork aside.

Lift the inner pot out (it's hot, so wear oven mitts!). Remove as much pork fat/grease as possible from the liquid by using a fat separator or by spooning it off the top. **Reserve 1 Tablespoon of the fat/grease; set it aside to be used later (discard remaining fat/grease).** Pour remaining juice/spice liquid back into the inner pot. Stir in the shredded pork until combined. Place inner pot back in the Instant Pot. Lock the lid back in place, flip the Pressure Release knob to VENTING and push the KEEP WARM button. **This keeps the pork carnitas mixture warm for as long as 10 hours (in case you prepare it early in the day).

Ten minutes before serving, put the reserved Tablespoon of pork grease/fat in a large skillet (use cast iron if you have it). Heat the fat on Medium-High. Use a slotted spoon to transfer shredded pork from Instant Pot into the skillet, spreading it out evenly. Cook the pork for 8-9 minutes, stirring occasionally, until it's browned and slightly crisp. If the pork dries out too much, add a small amount of the remaining liquid in the pot, and stir it in.

Prepare taco shells (your preferred method). Fill taco shells with carnitas mixture, top with chopped onions, cilantro and taco sauce, as desired. Serve and enjoy!