Combine lamb, salt, pepper, marjoram and rosemary in medium bowl. Mix with hands until well mixed. Cover and refrigerate for at least 1 hour or up to overnight.
Process the onion in a food processor for 10 to 15 seconds and turn out into the center of a tea towel or a few paper towels. Gather up the ends of the towel and tightly squeeze until almost all of the juice is removed. Discard juice.
Place the cold meat mixture into the bowl of food processor with the drained onion, garlic, and bacon. Process until a smooth paste is formed, about 1 minute total. Stop the processor to scrape down the sides with rubber spatula, as needed.
Form the meat mixture into meatballs, about 2-inches in diameter, setting aside on a sheet or a plate.
Stovetop: Heat oil in a large skillet, pan or cast iron skillet over medium-high heat. Once hot, gently lay the meatballs into the pan to begin cooking, do not overcrowd the pan, you don't want them touching. Cook 3 to 4 minutes on each side, cook until browned on all sides and cooked through and no longer pink inside. Add additional oil to the pan, as needed. Cooking time can vary based on the size of the meatballs.
Oven: Preheat the oven to 425ºF. Lightly grease a lined baking pan or line with parchment paper. Arrange the meatballs on the pan, giving them ample room so they aren't crowded and bake for 12 to 15 minutes, or until fully cooked through and no longer pink inside, rotating the balls every few minutes so they brown evenly on all sides. Cooking time can vary based on the size of the meatballs.
Notes
smoked bacon will affect the taste slightly. Additionally, best to know the bacon you are using in the recipe, as particularly salty bacon will result in VERY salty meatballs.