Combine salt, paprika, thyme, pepper, garlic powder, and sage in a small bowl.

Pound thicker end of chicken breasts to about 1-inch thickness. Sprinkle with seasonings and rub on both sides.

Turn on a multi-functional pressure cooker (such as Instant Pot®) and select Saute function and high heat. Heat olive oil and cook chicken breasts until browned, 2 to 3 minutes per side. Transfer chicken to a plate. Add chicken stock to the pot, scraping up any browned bits off the bottom. Turn off the pot. Place a trivet inside the pot and lay chicken breasts on top. Close and lock the lid. Select high pressure according to manufacturer’s instructions; set timer for 5 minutes. Allow 10 to 15 minutes for pressure to build.

Release pressure using the natural-release method according to manufacturer’s instructions, for 10 minutes. Switch to the quick-release method according to manufacturer’s instructions to release remaining pressure, about 5 minutes. Unlock and remove the lid. Remove chicken to a clean plate and cover with foil to keep warm.

Combine water and cornstarch in a small bowl and stir to dissolve. Switch pot to Saute function and medium heat. Slowly whisk in enough of the cornstarch mixture to thicken the gravy to your desired consistency. Season with salt and pepper. Remove from heat and serve gravy over chicken breasts.