Add ¼ cup neutral-flavored oil, 4 tablespoons fresh lime juice, 4-5 tablespoons fresh orange juice, 2 tablespoons minced garlic, ½ cup chopped fresh cilantro, 1 teaspoon salt, ½ teaspoon ground cumin, 1 teaspoon chili powder to medium bowl. Whisk together until combined. Pour into large ziploc bag.
Whisk ingredients together until fully combined. Transfer marinade large food-safe sealable bag.
Add 1 ½ pounds flank steak to bag with marinade. Remove all air from bag and seal bag closed, then flip and shake bag to coat steak in marinade.
Place bag in refrigerator and let steak marinate 30 minutes.
Toward end of 30-minute window, set Instant Pot to Sauté mode. Add 2 tablespoons neutral oil to Instant Pot and heat oil until shimmery.
When oil is hot, remove flank steak from bag and place steak directly in Instant Pot. Set bag aside - do not discard marinade.
Brown flank steak 2 to 3 minutes, then flip steak over and brown 2 to 3 minutes on other side. Repeat until flank steak has been browned on all sides.
Once steak is browned on all sides, turn off Sauté mode. Pour reserved marinade from bag into Instant Pot, covering flank steak evenly.
Secure lid on Instant Pot with valve in Sealing position. Set Instant Pot to Manual High Pressure mode and set cook time to 2 minutes. Instant Pot will pressurize, then 2-minute cook time will begin.
When 2-minute cook time ends, carefully Quick Release internal pressure. Use caution as escaping steam will be very hot.
Once pressure has released, carefully remove lid and set aside. Transfer flank steak to cutting board and let steak rest 5 minutes. After 5 minutes, slice flank steak into thin strips, cutting against grain of meat.
When flank steak has been sliced as desired, serve flank steak warm with preferred sides.