Combine all ingredients except tortillas in a slow cooker. Cook on low 6 hours or on high 4 hours. Shred chicken with two forks.
Fill tortillas with chicken mixture. Top with additional toppings, if desired.
To use as a freezer meal, combine all ingredients except tortillas and optional toppings in a one gallon zip top freezer bag. When ready to use, place frozen meal in slow cooker and cook for 6 hours on high or 8 hours on low. Shred chicken. Fill tortillas with shredded chicken mixture and optional toppings.
Add all ingredients except tortillas and optional toppings in Instant Pot. Lock lid. Set valve to sealing. Program for manual-high, 22 minutes. Shred chicken. Fill tortillas with shredded chicken mixture and optional toppings.
Note: if freezing for the Instant Pot, freeze in a freezable container that fits inside the Instant Pot, see notes.
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