Cut celery and carrots into pieces. If using onion skins, give the outer layer a rinse. Cut onion into wedges.
For a fresh carcass and wings: Heat oven to 375ºF. Arrange cut vegetables in the bottom of a roasting pan and place the turkey pieces on top. Add ½ cup water and roast until turkey and vegetables are just browning, about 40 minutes. Transfer everything to a 6 to 8 quart Instant Pot or multi cooker. Follow from step 4.
For a roasted carcass and parts: Place turkey parts and cut vegetables in a 6 to 8 quart Instant Pot or multi-cooker.
Add the herbs, peppercorns, and 2½ quarts of cold water. Seal lid and set on High pressure for 1 hour 30 minutes (90 minutes) or the soup/broth setting. After cooking let it naturally release for 30 minutes.
Carefully remove large pieces of bone, meat, and vegetables with tongs and discard. Place pot insert in an ice bath (a bowl of lots of ice and water) and stir occasionally until broth is cool about 30 minutes.
Pour cooled broth through a fine-mesh strainer into jars or containers to store. Discard all solids.
Notes
Notes: After the broth has chilled in the fridge, you can spoon off the solidified fat on the top and discard. If you don't have a fine-mesh strainer, place several layers of damp cheesecloth in a colander and pour broth through that, into a bowl, to strain small bits out. Storage: Broth can be frozen in freezer containers or freezer quart bags for up to 6 months. Broth can be kept in the fridge for up to 2 weeks.