Combine scallions, garlic, pepper flakes, ginger, water and soy sauce in a medium bowl.
Pat dry tofu slices or drain the water by putting the slices on a cutting board and leaving them slanted against something underneath for about half an hour.
Heat skillet or pan on medium heat. Brown tofu slices on both sides. This is the hard part. Tofu will undoubtedly stick to the pan if not careful. If you have a ceramic coated non-stick pan, this will be a piece of cake. I have stainless steel pan and it can be a disaster so I heat the pan hot, add oil before adding the tofu slices. And I make sure to tilt the pan to get the oil underneath the tofu so that they won't stick. Make sure NOT to flip the tofu too many times because they will crumble. Just lift the edges a little so that oil can get underneath them. Browning one side should take about 5 minutes or so, depending on your stove. Then, turn them over carefully to brown the other side. When both sides are brown, put the tofu pieces on a single layer.
Add the fried tofu in a medium sauce pan. Then, spoon the seasoned soy sauce mixture on top. Add more tofu on top of the sauce, and then, sauce. Repeat until soo the tofu pieces are seasoned with soy sauce.
Bring the pan to boil on medium heat. Once the soy sauce boils, reduce the heat and simmer for 5 minutes. Garnish with remaining black sesame seeds and serve while it's hot.