Preheat the oven to 450°F. Line a baking sheet with heavy-duty foil, dull side up, spray with nonstick cooking spray or brush the pan with oil, pour ½ cup of the panko crumbs onto the prepared pan and set aside.
In a large mixing bowl, whisk together the all-purpose flour, water, salt, and granulated garlic until smooth. Add the cauliflower florets into the bowl and gently toss to coat thoroughly. Use a slotted spoon to transfer the cauliflower to the prepared pan over the panko crumbs. Scatter the remaining panko over the cauliflower and toss to coat then spread the florets out so there is some space for air to circulate around them in the oven.
Bake for 25-30 minutes, or until the cauliflower is tender, and the coating is set and the crumbs are deep golden brown in places.
In a large skillet, combine the honey, teriyaki sauce, garlic, ginger, and -if using- the crushed red pepper flakes over high heat and bring it to a boil. Use a skillet to transfer the crispy cauliflower to the pan and toss gently to coat. Serve garnished with green onions.
Store leftovers tightly wrapped in the refrigerator. You can reheat/recrisp these by heating briefly in a 350F oven on a greased and foil covered cookie sheet or in an air-fryer briefly.