Preheat grill for medium heat and lightly grease the grate.
Mix water, coconut sugar, and yeast in a measuring cup until well combined. Let stand until yeast softens and begins to form a creamy foam, about 5 minutes. Add avocado oil, salt, and Italian seasoning; stir well.
Combine cassava flour, arrowroot powder, and gelatin in a bowl. Pour in yeast mixture; stir with a wooden spoon until well combined. Add more cassava flour as needed, 1 tablespoon at a time, until a dough forms.
Divide dough into 4 equal portions; knead and shape into balls. Dust a piece of parchment paper with arrowroot powder; place 1 dough ball on top and generously dust the top. Cover with another piece of parchment paper; roll out into a 4-inch pizza crust. Repeat this step with remaining dough balls.
Remove top parchment paper. Grease top of each crust with coconut cooking spray; flip and place crusts on the grill, greased-size down. Cook until golden brown, about 7 minutes.