Preheat oven to 350°.
Peel and grate potatoes. Mix together with salt and drain in a colander for 10 minutes.
Press potatoes against colander sides to eliminate moisture.
Place parchment paper sprayed with cooking spray on a small 12" x 8" pan or pizza pan.
Spread potatoes out on pan to form a crust.
Bake for 15 minutes. Remove from oven. Spray top with cooking spray and return to oven for 10 to 15 minutes or until golden brown.
Drain black beans. Place half the beans in a food processor with minced onion; blend until thick and creamy.
Spread bean mixture onto potato flatbread.
In a small skillet over medium high heat, cook bacon 5-7 minutes. Drain on a paper towel.
Sprinkle bacon on top of black bean puree.
In a small bowl, add remaining black beans, red onion and corn. Mix thoroughly and place on top of flatbread.
Return oven to 350°. Cook for 10 minutes or until beans and bacon are bubbly.
Slice roast beef into strips and place on top of potato flatbread.
Top with sliced jalapeño peppers and mozzarella cheese. Bake until cheese is melted, about 8 minutes.
Top potato flatbread with chicken and bacon, then sprinkle mozzarella cheese on top. Return to 350° oven and bake for 10 minutes or until cheese is melted.
Shred lettuce and mix with ranch dressing.
Dice tomato and set aside.
Remove flatbread from oven and top with lettuce and tomato.
Cook times vary for toppings and are in addition to the total time listed.