Put the brisket into a large zip top bag  

In a food processor, blend the celery, beets, pickling spice, salt, and coconut sugar, until the beets and celery are mostly broken down.

Pour the food processor mixture into the bag with the brisket and move it all around in the bag to coat. Remove the excess air from the bag and seal it up. Place in the fridge for at least 4 days or up to 10, massaging the bag every other day just to move around the marinade.

Remove the meat from the bag and fully rinse it off in the sink, discarding all the marinade.

Bring water to a boil on the stovetop. Add the additional pickling spice. Add the meat in and turn the heat to a simmer. Simmer on low for about 2 hours.

Taste a spoonful of the water to see if it tastes salty. If not, add some salt and pepper until it it salty like a rich broth. Add in the cabbage, carrot, and potato. The water should cover these veggies, so add a little more if needed. Continue to simmer on low for another hour until the meat and veggies are tender.

Carefully remove the meat from the pot and allow it to cook for 5 minutes. Meanwhile, remove the veggies with a slotted spoon and plate them.

Slice the brisket into medium thin slices against the grain and serve them over the veggies.