Cut the cauliflower in large florets. Transfer to a large bowl and set aside.
In a small bowl, combine the celery salt, oregano, cumin, onion powder, garlic powder, paprika, cayenne, salt, and pepper. Mix well.
In a medium bowl, add half of the spice mix to the flour.
Add the cornstarch and mix.
In a separate medium bowl, combine the soy milk, apple cider vinegar, and hot sauce. Whisk.
Pour the remaining spice mix over the cauliflower florets and mix.
Pour the milk mixture over the cauliflower and mix well until they are coated.
Cover with plastic wrap and chill for 1 hour minimum.
Heat the vegetable oil in a large pan until it reaches 350°F (180°C).
Toss each cauliflower floret in the flour mixture until well-coated, shaking off any excess. Dip them back in the remaining soy milk mixture in the bowl where they marinated, then again in the flour mixture.
Fry the cauliflower for 4-5 minutes, until golden brown and crispy.
Drain the pieces on a wire or paper towels. Let cool 5- 10 minutes before serving.