Line a baking sheet with a clean kitchen towel. Spread out the the soybean pulp over the kitchen towel and let it dry for about 1 hour at room temperature.
Next, transfer the soybean pulp to a mixing bowl. Add the white vinegar and stir using a wooden spoon to combine. Sprinkle the tempeh starter and stir again.
Prick a small freezer bag with a thin fork (or toothpick) 8-10 times to create small holes in the plastic bag. Add the soybean mixture to the freezer bag and pack it tightly into a loaf of about 1-inch thickness. I usually just fill half of the bag and fold it in half.
Add about 1 cup of water to the Instant Pot liner. Place the loaf on top of the steam rack, making sure it doesn't touch the water. Close the Instant Pot with the lid.
Set on yogurt mode "Less" for 20 hours. After 20 hours, you should see some while mold. Use a paper kitchen towel to remove the excess condensation on the lid and on the bag. Close the Instant Pot with the lid again and leave it inside for another 15-20 hours. If your kitchen is cold, turn the Instant Pot on yogurt mode again.
Check again after that, the mold should have grown even more. At this point, if the loaf is firm and fully white, you can remove it from the plastic bag and use immediately, or keep in the refrigerator for up to 7 days. If your loaf is not fully covered with white mold, place it in a warm room or next to a heat source for another 10-15 hours, the mold will keep growing.
Use the tempeh in curries, burgers, stir-fries, etc!