If you are using a whole cauliflower head, remove the leaves off the cauliflower and cut off the florets from the roots. Use a cheese grater or a food processor with a grater attachment, and grate the cauliflower into the size of rice.
Add almond milk, coconut sugar, cinnamon, nutmeg, and vanilla extract to the Instant Pot and stir together.
Add the riced cauliflower on top of the liquid.
Seal the lid, make sure the pressure valve is set to close, and set the Instant Pot to "Manual" for 2 minutes.
Once it finishes to a beep, immediately release the pressure valve and open the lid.
Sprinkle tapioca starch over the "oatmeal" and stir until thickened. Add more tapioca starch if you prefer the texture a bit thicker.
Transfer to bowls and top with nut, seeds, and/or your favorite toppings. Serve warm or chilled.
If you are making this ahead of time, don't add the toppings until you are ready to eat it.