Turn your Instant Pot to the "sauté" setting and wait for it to heat up.
Pat the beef roast as dry as you can with a paper towel. Season generously with kosher salt (about 1 tablespoon) and black pepper (about 1/2 tablespoon).
Add 2 tablespoons olive oil and brown the beef roast on all sides, about 3 minutes per side. Remove to a plate or shallow bowl (make sure it has enough depth to catch any runaway juices).
Add 2 tablespoons olive oil to the instant pot and add the onions. Sauté until softened and starting to brown (about 5 minutes).
Add the red wine to deglaze, using a wooden spoon to scrape up any browned bits stuck to the bottom of the pot. Continue cooking on the "sauté" function until almost all liquid has evaporated from the wine (about 5 minutes).
Turn the sauté function off. Add the carrots, rosemary sprigs, and thyme sprigs to the instant pot and stir. Place the beef roast on top, along with any juices from the plate. Pour the beef broth on top.
Place the wire rack insert that came with your instant pot on top of the beef, and place the potatoes on top of it.
Cover the instant pot and make sure the sealing valve is set to "sealed." Set the instant pot to manual on high for 60 minutes.
Allow the pressure to release naturally for 10 minutes, then use a wooden spoon to turn the sealing valve to "venting" to release the rest of the pressure.
Remove the potatoes to a large bowl and the beef to a platter or rimmed baking sheet (something that will catch the juices). Remove the vegetables with a slotted spoon and place with the beef, and discard the rosemary and thyme sprigs. Shred the beef into large chunks with two forks.
Mash the potatoes with a potato masher and add the remaining 1/4 cup olive oil to them. Add 1 cup of the drippings from the bottom of the instant pot and continue mashing until desired consistency is reached. Season to taste with salt and pepper, if necessary.
Mix the corn starch with 1/4 cup of water to create a smooth slurry. Turn the Instant Pot to the "sauté" setting again. Once the drippings are boiling, stir in the corn starch slurry until thickened (about 2 minutes). Season to taste with salt and pepper.
Serve the mashed potatoes topped with the pot roast and carrots/onions, topped with the gravy.
You can read more about Bottom Round Roast, and other cuts of beef, on the ButcherBox website.
More commonly, chuck roast is used for pot roast. You can feel free to use this cut, or brisket as well. Here's a great primer on the best cuts of beef for pot roast.
This recipe is 100% paleo/whole30 compliant except for the cornstarch. Omit it and serve with drippings rather than making a gravy (or use arrowroot powder) to make it compliant.
I made this recipe in my 6 qt. Instant pot. It should work the same in an 8 qt., but you may need to cut the ingredients in half for a 3 qt. mini.
The provided nutrition information does not include any added sodium from seasoning to taste, any optional ingredients, and it does not take brands into account. Feel free to calculate it yourself using this calculator or by adding the recipe to Yummly.