Add the cassava flour, salt, baking soda, and cream of tartar to large bowl and mix together.
Add the oil and knead into the dry ingredients for a minute. The mixture will be dry and crumbly.
Add the warm water and knead together for 2 to 3 minutes. At first the dough will be wet and sticky, but as the cassava flour absorbs the water it will become dryer and more pliable. The texture should be similar to soft Play-Doh. If it's too sticky, add a bit more cassava flour. And if it's too dry, add a bit more water.
When you have a mound of dough, roll it into a log shape in the bowl (like a tube of cookie dough). Then, slice it into 6 pieces. Take each piece and roll into a ball.
If you have a tortilla press, take each ball of dough, place it between two pieces of parchment paper and press into a flat tortilla (this method is much easier). Without a tortilla press, take each ball of dough between two pieces of parchment paper and roll out into an approximate 6-inch circle.
Heat a non-stick pan or flat griddle on medium-high heat. As the dry pan heats up, place one tortilla in the pan and cook for approximately one minute. Flip the tortilla and cook the other side for an additional minute. Continue cooking all tortillas and transfer to a plate with a paper towel.
Eat immediately or freeze in batches for future use.