In your gallon sized baggie, mix the flour, salt and sugar.
Add in the yeast and mix again.
Add the water and olive oil to the bag and close the top. Mix well again.
Knead the closed bag for a few minutes (about 5) until it's well mixed and looks like it's not super sticky.
Coat your cast iron griddle or skillet with olive oil, and coat your hands as well. This helps to keep the dough from sticking to you.
Take the dough from the bag and press it down into the bottom of the pan.
If cooking in an oven, preheat the oven to 500 degrees, assemble the pizza and bake 10-12 minutes.
If cooking over a campfire, cook the crust until firm. Top with sauce and toppings and then loosely cover the top with aluminum foil. Cook about 5 minutes or so until the cheese has melted and toppings are warmed.