The day before you plan to cook: combine the apple juice, soy sauce, onions, garlic and sesame oil in a gallon-size resealable food storage bag. Pierce the beef chuck roast all over with a fork to enhance marinade absorption before adding it to the bag, then seal and refrigerate overnight.
The next day, add the neutral oil to the pressure cooker to cook over medium heat (with Instant Pot, press the 'Saute' button to begin cooking at medium saute heat). When the oil is hot, place the meat into the cooker (reserving the marinade) and brown well on the top and bottom surface (about 4-5 minutes on each side).
After both sides are browned, pour in the marinade and cover the pressure cooker with the lid, ensuring that the valve is in sealing position. Cook under high pressure for 60 minutes (with Instant Pot, press ‘Cancel’ to stop saute mode before closing the lid, then press ‘Manual’ and "+" to select 60 minutes).
When the cooking time is up, allow at least 10 minutes for the pressure to release naturally. Open the lid and carefully transfer the roast to a plate to rest for an additional 5-10 minutes before slicing against the grain into approximately 1/4 inch thick pieces.
Serve the sliced beef ssam-style (as lettuce wraps) with fresh lettuce leaves, cooked rice and kimchi, along with any other favorite "banchan" (small plates) or sauces. Store leftover beef in an airtight container, with cooking liquid poured over the top to keep it moist.