Combine the matzo meal, salt and garlic powder in a medium mixing bowl. Using a fork, whisk in the eggs. Add the herbs, chicken fat or neutral oil and seltzer; stir together until just combined (don’t overmix). The matzo mix will expand and firm up as it sits.
Refrigerate until the matzo mixture has firmed up, at least 1 hour (you can also do this overnight or a few days in advance).
Bring a large pot of well-salted water to a boil. Take a rounded tablespoon of the matzo ball mixture, roll it into a 1-inch ball (wet hands help – the mixture is sticky), and set aside on a plate (you should have about 24 matzo balls – they will double in size, so don’t worry if they look quite small). Alternatively, you can roll and plop the balls directly in the water.
Gently add the gluten-free matzo balls to the boiling water and cover with a tight fitting lid. Cook, covered, over medium heat until floating, puffed to double their size, and cooked through, 15 to 25 minutes (check at the 15 minute mark, but don’t peak before then). The matzo balls are done when they are uniform in density and texture all the way through, lighter in color and fluffier compared to the raw matzo mix. You can always put them back in to cook longer and soak up more broth. If you see some stray strands in the water from the balls, don’t worry.
Either save the matzo balls and serve later, or divide between bowls and top with my Jewish chicken soup (also known as the best matzo ball soup base). They keep decently well in one layer in the fridge for a few days.