Heat a large frying pan over medium high heat with a splash of olive oil. Add the beef and cook about 8 minutes to brown on all sides. Strain any excess fat from the pan.
Add in the olive oil and onions and cook another 5 minutes. Add in the garlic and cook 2 minutes. Add in the crushed tomato, oregano, and pepper flakes and stir to combine. Bring to a simmer and cook 10 minutes.
Preheat oven to 400. Put a small layer of sauce in the bottom of your lasagna pan. Add a sheet of pasta, some ricotta, mozzarella, and more sauce. Repeat until you fill the pan or run out of sheets. Go heavy on the sauce, because the no-boil noodles will absorb a lot of the sauce as it cooks.
Bake for about 30 minutes until bubbly and brown on top. Allow to rest 10 minutes before cutting and serving.