Not at all. It's easy. The sold weight from the store is ample enough for your calculations. I like buying the bright red sockeye salmon to use for it instead of the pink slabs of grocery store Atlantic salmon. You're much more likely to get it in matching right/left fillets, which makes things really easy.
There are two, maybe three parts to the process. The salt cure. The dry. The smoke. Smoke is optional, but no reason not to this time of year.
Equal parts kosher salt + brown sugar. The most amount of each I've used was 1.5% by weight. Work in grams. I've done a higher percentage before and it was unpalatable. Fish takes on salt much easier than other meats, and I've found 1.25% - 1.5% is just right for cured salmon.
I hand crank as much black pepper on the fillets as my forearms will allow. Then take your calculated salt/sugar mix and cover each fillet. Reserve about 1/4 of it so you can get the outside skin. Zest a lemon and zest a lime onto each fillet over top of the salt/sugar cure. Maybe lightly press it into the flesh, but not necessary. Finally, et a bunch of fresh dill and lay it on the slab. Here's where I like to get matching right/left fillets. Sandwich them together, use the rest of your cure on the outside skin of each side, then wrap securely in plastic wrap. It's going to leak a lot of water, so definitely put it on a big cookie sheet when you put it in the fridge.
I've wrapped some bricks in plastic wrap, and use them to weight down the thickest portions of the fish sandwich. Put it in the fridge for a day. Flip and refrigerate the next day. Pull it halfway through the third day. Anything more will be too much. Unwrap the fish and rinse off all the granular stuff. Pat the fillets dry, and place on a rack back in the fridge for a day to dry.
After drying for a day, it's ready to eat. Or, if you want to smoke it, smoke it first. But it's not a hot smoke. One or two burning coals and sprinkle some sawdust on there. Do it on a cool/cold day. The point is not to heat the smoker up past about 80°. Wispy smoke for a long time goes a whole lot better than a hot fire.