Preheat your oven to 400°F (200°C). Line a baking sheet with parchment paper.
Drain the canned chicken thoroughly. Place the chicken on a clean kitchen towel or several layers of paper towels and squeeze out all excess moisture until it is as dry as possible. This step is critical for a crispy crust.
In a medium bowl, combine the dry chicken, the egg, grated Parmesan cheese, 1/2 cup of the shredded mozzarella, Italian seasoning, and garlic powder. Use your hands to mix until a uniform, sticky 'dough' forms.
Transfer the chicken mixture to the center of the prepared baking sheet. Press it out with your hands or a spatula into a thin, even circle or rectangle, approximately 1/4-inch thick.
Par-bake the crust in the preheated oven for 15-20 minutes, or until it is firm and golden brown around the edges.
Remove the crust from the oven. Spread the keto-friendly marinara sauce evenly over the surface, leaving a small border. Sprinkle with the remaining 1/2 cup of mozzarella cheese.
Arrange the pepperoni slices on top of the cheese. Add any other desired low-carb toppings.
Return the pizza to the oven and bake for an additional 5-10 minutes, until the cheese is bubbly, fully melted, and slightly browned.
Let the pizza rest on the baking sheet for at least 5 minutes before slicing. This allows the cheese to set and ensures clean cuts. Slice and serve immediately.