Choose a squash that will fit in your Instant Pot. For a 6-quart Instant Pot, make sure the squash is not longer than 8 inches (20 cm). We found 4 pounds to be the maximum size squash that would fit.
Carefully halve spaghetti squash lengthwise using a sharp knife. I find the best way to do this is inserting the very tip of a very sharp large knife into the side of the squash (lengthwise) and pushing it all the way through to the other side. Rock the knife back and forth to cut one half all the way through, then repeat on the other side.
Use an ice cream scoop (or sharp spoon) to scrape out the seeds and most of the stringy parts.
To a 6-quart or larger Instant Pot, add 1 cup (240 ml) water.
Place trivet in Instant Pot and add halved and deseeded spaghetti squash sideways, facing up so that both halves fit. Seal with lid.
Press “PRESSURE COOK,” make sure it is set to HIGH, then adjust time to 8 minutes. Allow Instant Pot to pressurize (this takes ~5-10 minutes).
Once the timer goes off, press the quick release. Carefully remove lid once steam has fully escaped. Use a fork or knife to check if the squash is fully cooked. Once cooked, it should easily pierce the skin and flesh. If not fully cooked, cover with lid and allow to continue steaming on “KEEP WARM” for 5-15 minutes or until tender.
Once slightly cool, press “CANCEL,” remove squash, flip flesh-side up and use a fork to scrape out the strings.