Set the Instant Pot on Saute and add the olive oil. Heat for 2-3 minutes.
2 Tablespoons olive oil
Brown the leg of lamb in the Instant Pot, turning to get all the side.
Take the lamb out of the Instant Pot. Add the chicken broth and use a wooden spoon to scrape the bottom of the Instant Pot to deglaze it and remove any browned bits of lamb.
1 cup chicken broth
Add the carrots and onion to the Instant Pot and put the lamb on top.
3 carrots, 1 onion
Put the lid on the Instant Pot and close the valve. Set the pressure cooker to Manual, high pressure, for 30 minutes.
When the pressure cooker is done let it release pressure manually for 10 minutes. Then release the remaining pressure.
Check the temperature of the lamb using an instant read thermometer. If it is 140 F take the lamb out and cover it with foil to rest while you cook the potatoes. If the lamb needs a little longer leave it in the Instant Pot.
Add the potatoes to the Instant Pot. Put the lid back on and set the Instant Pot on Manual for 8 minutes. When it is done let the pressure release naturally for 5 minutes, then release the rest of the pressure.
2 pounds small red potatoes
If the lamb needed more cooking let it rest for 10 minutes before slicing and serving.
Slice the lamb and serve it with the potatoes, carrots and onions.
Notes
I make and test my recipe in a 6 quart Instant Pot. Using a different size or brand might effect your results. If you are using an 8 quart model I'd suggest increasing the broth to 1 1/2 cups.