Let me clarify: You can't cook badly shaped bacon. All bacon shapes are delicious, but sometimes you want the bacon to be at the center of your presentation. Whether you want perfect bacon squares for tiny BLTs or perfectly straight strips to accompany a classy breakfast platter, keeping bacon flat and cooking it evenly can be a pain in the ass.
Fortunately, we have ways of dealing with unruly pork. Line a sheet tray (or jelly roll pan, or a cookie sheet -- whatever you have that's large, flat, and lipped) with foil. This makes cleanup fast and easy, and also lets you quickly transfer the rendered bacon fat to a container for storage so that you can cook everything -- and I mean everything -- in bacony goodness.
Lay a wire rack on the lined tray. This keeps your bacon off the surface of the metal. The reasoning here is the same as with a roast: You want the air to be able to circulate around the bacon, allowing it to cook quickly and evenly. Lay the bacon out single file, no overlap. Sometimes, this setup is enough.
Most of the time, bacon will come out flat and browned and beautiful just like that. If you have particularly thin or fatty pieces of bacon, however, it can still curl up on you as the water evaporates from the meat and the belly fat renders. To combat this, simply lay another wire rack face-down on top of the bacon. Bake at 350 or 375° F until done, maybe ten to twenty minutes depending on how crispy you want it. Boom. Done.
This is also particularly useful for candied bacon. Of course, like all bacon, it should be drained over or patted down with paper towels to remove excess grease. If you're looking to do precision cuts, don't cook the bacon to the point of crumbly crispy -- leave a little flex. You can always finish it to your desired crispness once you've cut it into the pieces you want.