First, wash your blueberries, then drain off any excess water and add them to a clean Instant Pot.
Then add about 1/4 cup of lemon juice (the juice of one lemon), the zest of one lemon, and honey. Mix this all together and cover your Instant Pot, but do not turn it on. Let this mixture sit for 30 minutes. This will allow the blueberries to release some of their juices.
When 30 minutes have elapsed, give the mixture a stir, then close and seal your Instant Pot.
Set the Instant Pot for 2 minutes on Manual Mode/High Pressure. It will take 5 - 10 minutes to come to pressure, then it will cook for 2 minutes. I like to cook my blueberries longer than I would for a strawberry jam to break through the outer skin and soften them up so you don't get chunks of chewy skin.
When two minutes are up, let the Instant Pot sit and naturally release for 15 minutes. (If you have a "Keep Warm" setting, you can just leave that on and use it as a timer!)
While 15 minutes is counting down, mix your arrowroot and water together to form a slurry.
After 15 minutes, release any remaining pressure manually, then open your Instant Pot and set it to the "Sauté" function. (Your jam will look really watery - this is okay!)
When the mixture starts to bubble, mix in your arrowroot slurry. Let this all bubble together for a few minutes then turn off your Instant Pot. Blueberry jam thickens up pretty quickly.
Blueberries don't really need to be mashed as you would other fruit - they will be pretty soft after cooking and will mash up just from being stirred.
Let the jam cool, then serve or transfer to jars - it will be pretty sticky and will thicken as it cools.