If using fresh thighs, pat them dry and season with salt and pepper or your preferred seasonings.
Set the Instant Pot to the Sauté setting and add the oil. When the oil is hot, sear the seasoned thighs skin-side down for 3–4 minutes until the skin is golden and crispy, then flip and sear the other side 3–4 minutes. Remove the thighs and set aside. (Skip searing for frozen thighs.)
Pour 1 cup of your chosen liquid into the pot and scrape up any browned bits from the bottom with a wooden spoon.
Place the trivet in the Instant Pot and arrange the chicken thighs on top of it.
Secure the lid and set the valve to Sealing. For boneless thighs, pressure cook on High for 8 minutes (fresh) or 12 minutes (frozen). For bone-in thighs, pressure cook on High for 10 minutes (fresh) or 15 minutes (frozen).
Allow pressure to release naturally for 5 minutes, then carefully turn the valve to Venting to release any remaining steam.
Check the thickest part of a thigh with an instant-read thermometer; it should read 165°F. If it's a little under, replace the lid and let it rest for 5 minutes, or pressure cook 1–3 minutes more if needed.
Let the chicken rest 5 minutes before serving.