First, pour the milk into the inner pot of the Instant Pot. Turn the Instant Pot to the "High" Yogurt setting, which will bring the yogurt to boiling temperature for 1 minute and then end. This takes about 10-20 minutes, though I've never timed it. Keep covered and stir occassionally with a very clean instrument (not wood - use either metal or silicone).
While that happens, prepare an ice bath to cool the yogurt by adding ice to a very large bowl.
Once milk has boiled, remove the inner pot carefully and place in the ice bath. Add some cold water to allow the inner pot to submerge slightly, if needed. Stir the milk and periodically check the temperature until it reaches about 110ºF.
Remove about ½ cup of milk to a smaller bowl or 2-cup measuring cup. Add the culture and stir well until disolved. Add this back to the larger pot and stir well.
Dry the outside of the inner pot thoroughly, so as to not damage the Instant Pot. Place this back in the Instant Pot. Set the Instant Pot to medium yogurt setting and allow to ferment, with the lid on, for somewhere between 4-8 hours. With the Straus culture, after the first time, it takes about 6 hours. You are looking for the yogurt to be thick and for it pull from the sides nearly in a block if you lift and tilt the inner pot to one side. It should have a slight nearly clear, liquid layer on the top.
Cover well (consider using a sealing lid or wrap of some kind) and then place in the fridge to cool for several hours to further firm up. When cooled, transfer to the weck jars, but make sure to save at 2-3 tbsp separately for the next time you make yogurt.