Place a trivet in the inner pot; add 1 cup of water. Spray a 7" baking pan generously with cooking spray on bottom/sides.

Place blackberries in a medium bowl. NOTE: If using frozen berries, do not thaw; put them (still frozen) in the bowl. Add granulated sugar and lemon juice. Gently stir until combined. Pour berries into baking pan; spread to cover the bottom.

In a separate bowl, stir oats, flour, brown sugar, cinnamon, nutmeg and salt together. Add melted butter; stir until streusel is crumbly and holds together when pinched. Spread streusel over the blackberries, covering the fruit.

Cover baking pan with foil, crimping the edges firmly around the pan to seal. Lower pan onto the trivet in the inner pot.

Put the lid on the Instant Pot; lock it in place. Turn the steam release valve to SEALING. Select the MANUAL button (high pressure); set the timer for 10 minutes. It will take 7-10 minutes to reach full pressure before cooking program/timer begins. When cooking program ends, the machine should beep.

Let the pressure release NATURALLY (do nothing) for 5 minutes, then flip pressure knob to VENTING to release all remaining steam. Pressure gauge will drop back down once all steam is gone, indicating it's safe to open the lid. Remove baking pan from the inner pot. The blackberry crisp is done cooking and can be cooled slightly then served. *I prefer to brown and "crisp up" the topping a bit more so I do 1 more step before serving. NOTE (optional): If you want streusel to be browner, turn on your oven broiler while the IP is venting. Once baking pan is removed from the IP, place it on a rack about 4" under the broiler. Keep an eye on it- after 1-2 minutes under broiler, streusel should be browner and crisper!

Let blackberry crisp cool for a few minutes (it will firm up as it cools), then scoop out warm portions into bowls (5 small servings). Add a scoop of vanilla ice cream (if desired) and serve. Enjoy!