Measure out all of the spices. If your coriander seeds or fennel seeds are whole, lightly crush them with the bottom of a heavy pan or in a mortar and pestle until cracked but not powdered.
2 teaspoons dried coriander seeds, 1/2 teaspoon ground fennel seed
In a medium bowl, combine the kosher salt, black pepper, garlic granules, onion granules, crushed red pepper flakes, paprika, dried dill, crushed coriander, mustard powder, and ground fennel (if using). Stir with a spoon or small whisk until evenly mixed.
2 tablespoons coarse kosher salt, 2 tablespoons coarsely ground black pepper, 1 tablespoon garlic granules, 1 tablespoon onion granules, 1 tablespoon crushed red pepper flakes, 2 teaspoons paprika, 2 teaspoons dried dill weed, 2 teaspoons dried coriander seeds, 1 teaspoon mustard powder, 1/2 teaspoon ground fennel seed
Pinch a small amount of the seasoning between your fingers and taste it. Adjust by adding more crushed red pepper for heat or more dill or other dried herbs for extra herbiness, to suit your preference.
Pour the seasoning into a clean, dry glass jar or spice container with a tight-fitting lid. Label the jar with the name and date.
For best flavor, let the seasoning rest for at least 24 hours before using so the spices can mellow and meld together. You can still use it immediately if needed.
Use about 1 to 1 1/2 teaspoons of seasoning per 8-ounce steak, or about 1 to 1 1/2 teaspoons per pound of meat. Pat meat dry, season generously, and let sit 15–60 minutes before cooking. Also use on chicken, pork, salmon, tofu, potatoes, roasted vegetables, or even popcorn.