Cut the pork in half crosswise and season all over with the salt and pepper. Sprinkle with the cassava flour and dredge so that it is coated all over with the flour. Shake off any excess.
Press the ‘saute’ button and heat the Instant Pot. Add the oil and heat until very hot. In batches, sear off the pork so that it is golden brown on all sides, about 3 minutes per side. Set the browned pork aside.
Add the onion to the Instant Pot and saute, tossing, until slightly tender, about 4 minutes. Hit the ‘cancel’ button and nestle the pork back into the Instant Pot. Add the apple cider vinegar, the coconut aminos, and ½ cup of the prepared mojo sauce (reserving the rest for serving).
Securely fasten the lid on top of the Instant Pot, making sure the vent is sealed. Press the "manual" and then set the time to 70 minutes. Walk away from the Instant Pot and let it do its thing! Note: If your Instant Pot doesn't have a manual button, set it to 'high pressure.’
When the cook time is complete, release the pressure manually by carefully turning the valve. When all of the pressure has been released, remove the lid and transfer the pork to a rimmed baking sheet, leaving the liquid in the Instant Pot. Using two forks, shred the pork then add back into the Instant Pot.