Cook the sweet potato by baking it in its skin, if possible. Peel and separate 200 grams, leaving the rest aside for another purpose. Rice it into a mixing bowl.
Add salt to the riced sweet potato and mix it thoroughly with a spoon until smooth.
Add remaining ingredients and mix on medium to high speed with a dough hook until the dough is smooth and pulling away from the sides of the bowl, 10 minutes or so. It will be a wet, sticky dough but should eventually come together.
Transfer dough to an oiled bowl, cover with oiled saran wrap, and allow to rise in refrigerator overnight.
Remove from refrigerator, turn out onto a floured surface. Separate into 8-10 pieces of 130-150 grams each and roll into balls. Place balls on well-floured surface and flour the tops as well. Rest for 15 minutes.
Roll balls into circles of 5-6" that are 1/2-3/4" thick. Flour, cover, and allow to proof for 45 minutes to an hour or until 1 1/2" thick or so.
Cook bread on griddle over medium heat for 8 minutes per side, turning frequently to avoid burning on hotspots. Wrap finished flatbreads in a clean kitchen towel while cooking remaining pieces.