Heat the oven to 350°F. Remove the cauliflower leaves and tough base, rinse, drain well, and break into small florets.

Pulse the cauliflower in a food processor until the pieces resemble rice and remain separate rather than pasty. Measure 4 cups.

Put about 1 inch of water in a stainless stockpot and set a steamer basket above the water. Add the cauliflower rice, cover, bring the water to a boil, and steam for 5 to 6 minutes until the raw crunch is gone but the pieces remain recognizable.

Drain briefly, then squeeze 1 to 2 cups at a time in a thin cotton towel or cheesecloth until firm pressure produces little or no dripping. The cauliflower should feel damp and crumbly, not glossy or wet.

Beat the egg in a medium bowl until fully blended. Stir in the oregano and sea salt, add the squeezed cauliflower, and mix until evenly coated with no liquid pooling in the bowl.

Line an 11-by-17-inch rimmed sheet pan with parchment and coat it lightly with coconut oil. Spread the cauliflower mixture into one large, even crust with no thin gaps.

Bake for 20 minutes, until the top looks matte and the edge is set enough to slide a wide peel underneath without tearing.

Flip the crust with a wide pizza peel and bake for 20 minutes more, until the edges are golden-brown and the crust lifts as one piece.

Move the crust to a cooling rack so air can circulate underneath. Add separately cooked, well-drained toppings only after the crust is fully baked.