Rub Gluten Free Spice Mix generously all over the surface of your roast.
Select "Saute" setting on your Instant Pot. When the word "Hot" appears, add avocado oil. Sear the roast on each side to brown, about a minute per side.
Remove roast and set aside for a moment. Add water and stir to deglaze the pot.
Place Instant Pot trivet into the pot, and set the roast on it over the liquid. Set your pressure cooker for "High Pressure" for 50 minutes, or longer for a larger roast. (See chart above.)
When cooking time is up, allow the pressure cooker to naturally release for 10 minutes. Then open vent for quick release.
When your Instant Pot is ready to open (the little button has dropped down), remove the roast, and set it aside while you make the gravy. Then slice and serve.
Gravy
Pour liquid from bottom of Instant Pot into a measuring cup. After noting the amount, return it to the pot. Set Instant Pot at "Saute."
Measure enough cold water so that you will have a TOTAL of 2-cups liquid (when combined with previously measured hot liquid) into the measuring cup.
Whisk starch into the cold liquid so that no lumps remain.
When the drippings in the Instant Pot have come to a boil, whisk in the starch/cold water combination. Your gravy should thicken up immediately and be ready to serve. (If using arrowroot starch, cook it a little longer.)
Notes
If you've cooked a larger roast and have more than 2 cups of hot drippings, you can adjust the gravy recipe to make more. The important steps are that you should have 1 tablespoon cornstarch or arrowroot starch per each cup of total liquid and the starch MUST be smoothly blended into cold water.