Combine bulgur wheat, boiling water, and 1/4 tsp. kosher salt in a large bowl. Cover and let stand 1 hour or until water is absorbed. Meanwhile, cut carrots lengthwise into very thin, ribbon-like strips using a mandoline or Y-shaped vegetable peeler. Toss together bulgur, carrots, radishes, green onions, parsley, mint, lemon zest, lemon juice, and olive oil in a large bowl. Season with 1/2 tsp. freshly ground black pepper and 1/2 tsp. kosher salt. Cover and chill 2 to 4 hours. Fold in avocado and sunflower kernels. Add table salt and black pepper to taste.