Put the salt, sugar, and black pepper into a bowl and mix until evenly distributed. Spoon the mixture onto the exposed salmon flesh, making sure to cover as much of the exposed areas as possible.
Place the dill on top of the salmon. If the dill is too long to fit on top of the filet, then snap off the stems or fold the dill over.
Wrap the salmon, salt, dill sandwich up, tightly, in the plastic wrap. Take a second sheet of plastic wrap and wrap again. Wrap in foil. Place the package in a plastic bag so the liquid does not spill.
Refrigerate the salmon for at least two days. Remove the container from the refrigerator, open the package, remove the dill, and rinse in water. In short, just wash the gravlax. If any pieces of salt or pepper are stuck to the flesh, just wipe it gently off. Dry with a paper towel.
Slice thinly.