Cut the salmon in half cross-wise to get two square-ish pieces.
Mix sugar, salt, fennel and pepper together. Rinse and dry dill sprigs, leaving them intact.
Lay one skin-side-down into a glass loaf pan or other non-reactive dish at least 2″ deep.
Sprinkle evenly with half the salt mix, spread the dill sprigs over, sprinkle with remaining salt.
Lay the other piece of salmon on top, skin-side-up to make a “sandwich”.
Cover with plastic wrap and fit a tupperware or other container inside the loaf pan. Fill it with a heavy can or jar to weigh the fish down.
Refrigerate 3-4 days, turning the “salmon sandwich” every 12 hours or so. Every 16 hours is okay, too. After only the first day, there will be quite a bit of brine accumulated in the dish. Leave it there until serving time.
Eat after 3-4 days and store leftover gravlax sans brine in an airtight container.
I served with the following sauce: 2 tablespoons rice wine vinegar 2 tablespoons olive oil 1 tablespoon grainy mustard 1 teaspoon dill weed 1 teaspoon horseradish salt and pepper