In a small bowl, whisk together the matzo meal, baking powder, salt, and pepper. Set aside.
In a large bowl, whisk together eggs, seltzer water, and schmaltz or vegetable oil. Mix in the matzo meal mixture to the dried ingredients. Refrigerate uncovered for 30 minutes.
Using a medium cookie scoop, form Matzo balls into 1 1/2 inch balls, wetting your hands and roll them to finish shaping them. Rewet your hands as needed.
Meanwhile, divide the chicken stock evenly into 2 large saucepans. Add the matzo balls to one of the saucepans, cover, and simmer until they're cooked through about 1 hour. In the other saucepan, add the carrots, celery, and 1-2 sprigs of dill simmer until they're tender. Remove dill sprigs.
When the matzo balls are cooked, using a slotted spoon, add them to the saucepan with the cooked carrots and celery, then pour the matzo ball cooking chicken broth through a fine sieve into the saucepan with the cooked veggies and matzo balls. Add the chopped dill.
Ladle soup into individual bowls and serve. Garnish with chopped dill.