How do I make this into dough? Is this correct?
20 ounces of flour must refer to a weight of flour not volume. By weight, 20 ounces of flour should be more like 4 cups of flour.
Just did the math and assuming 4.5 ounces per cup of all-purpose flour, 20 ounces is just under 4 1/2 cups. However, this changes with different types of flour since different flours have different densities and different weights per cup as a result.