Combine gluten free Maseca corn masa flour, salt, oil and water. Allow to rest for 10 minutes to allow moisture to be fully absorbed. 

While dough is resting, oil and preheat griddle

After 15 minutes, turn dough out onto a non-stick surface, and knead until a ball of dough. Finally, form dough into 8 small balls. 

Flatten the dough, and lay on a non-stick surface. (I use a silicone mat.) Top the center with 1-2 tbsp of filling. Gently fold the edges in over the center, similar to filling a galette. Close any holes, and press gently with your hands to make a flat patty. 

Cook pupusas 3-4 minutes per side on your well-oiled griddle. Keep warm in a preheated oven (200*), on a cookie sheet, until all pupusas are made and ready to serve. 

Serve with a side of salsa and/or curtido. (Curtido recipe can be found on TheKitchn.)