Pour water into the bottom of an 6 quart (or larger) Instant Pot.
Place brisket into the pot (if the brisket has a fatty side, put it fat side down.)
Sprinkle spice packet on top of the brisket and place lightly smashed garlic cloves on top as well.
In a bowl or large ziploc bag, toss potatoes and carrots with oil and garlic salt. Place veggies around the sides of the brisket.
Lock lid on top of Instant Pot and pressure cook on HIGH for 45 minutes.
While the corned beef is cooking, begin making the cole slaw.
For the Irish Coleslaw:
In a large bowl, whisk together mayonnaise, honey, olive oil, Dijon mustard, caraway seeds, and season with salt (to taste).
Gently toss the dressing with sliced red and green cabbage and fresh parsley.
Cover and refrigerate until ready to serve.
To finish:
Once corned beef and veggies have finished cooking, allow the pressure to naturally release for about 10 minutes then release the valve and allow steam to escape.
Once steam has escaped, and pressure has released, carefully remove the lidPlace carrots and potatoes on a serving platter; cover with aluminum foil to keep warm.
Place corned beef on a large cutting board and allow to rest for 5 minutes. Slice corned beef against the grain and place on top of platter.