Add the masa harina to a mixing bowl.
Add the tamari and then add a little of the water at a time, stirring until is starts clumping together.
Add only enough water that it comes together into a ball and you can squeeze it together without it sticking to your hands.
Knead it for a couple minutes and place back into the bowl and cover with a towel.
Preheat your pan.
Divide dough into thirds. Take each third and roll it into a small tube about 4 inches long with your hands. Lay tube onto a piece of parchment paper and lay another piece of parchment on top. Using something heavy with a flat bottom like a small cutting board or baking dish to press the dough almost flat and then roll it gently with a rolling pin to the size and shape of a sandal.
Gently transfer base onto the preheated pan by pealing the parchment off the top, placing your hand flat on the surface, flip it over and peel off the bottom parchment and place base onto the pan. Cook for at least a minute or until it feels like you can flip it without it breaking. Cook on the other side for at least another minute.
Place finished bases on a plate and cover with a towel until you are ready to assemble.