Preheat oven to 500°F. Place pizza stone on lowest rack in oven during preheating.
Combine 1 cup all-purpose flour, cake flour, undissolved yeast, sugar and salt in a bowl. Add water and mix until well blended, about 1 minute. Add additional flour, if needed, to form a soft dough.
Knead** on a floured surface, adding additional flour if necessary, until smooth and elastic, about 4 minutes. Divide dough into 8-equal size portions. Cover dough while working with individual portions. (If not using Pizza Yeast, allow dough to rest for 10 minutes.)
Roll one portion of dough on floured surface into a 12 x 4-inch rectangle. The dough should be extremely thin at this point.
Place flat bread on a well-floured or cornmeal-dusted pizza peel, flat baking sheet or the back side of a jelly roll pan. Parchment paper (not waxed paper) also works. Make sure that the flat bread moves freely.
Combine pizza sauce, ketchup and mustard in a small resealable plastic bag; snip off corner of bag. Sprinkle 2 to 3 tablespoons cheese over pizza. Top with hot dog slices and about 1 teaspoon onion and pickle relish. Squirt ketchup mixture over pizza. Repeat with remaining crusts.
To bake, slide the flat bread off the pizza peel or baking sheet onto the preheated stone that is still in the oven (On most pizza stones, you should be able to bake 2 flat breads at the same time). Use a long-handled spatula to help transfer the bread if needed. Bake 3 to 5 minutes or until flat bread is lightly browned.
When the flat bread is done, remove it from the oven with a pizza peel. You can also use a spatula or tongs to gently transfer the flat bread to a cutting board, pizza pan or cookie sheet for serving.
Allow the oven to cool before removing the pizza stone and follow the manufacturer’s directions for cleaning.
*If you don't have a thermometer, water should feel very warm to the touch.
**To knead the dough, add just enough flour to the dough and your hands to keep the dough from sticking. Flatten dough and fold it toward you. Using the heels of your hands, push the dough away with a rolling motion. Rotate dough a quarter turn and repeat the "fold, push and turn" steps. Keep kneading the dough until it is smooth and elastic. Use a little more flour if dough becomes too sticky, always working the flour into the ball of the dough.
NOTE: While a pizza stone is preferred for making flat bread, you can also use a heavy baking sheet. Preheat the baking sheet in a 500°F oven for 10 minutes. Transfer rolled flat bread to hot baking sheet using the directions above for transferring the dough to a pizza stone.