With your hands. You can shape a meatloaf using a loaf pan or casserole dish. Or you can make a sheet pan meatloaf without a loaf pan. Simply dump the meatloaf mix onto a greased or parchment lined sheet pan. Using your hands start gently pressing the meat together until a loaf is formed. Press down or push together cracks in the loaf for a smooth meatloaf that will stay together. Using the sheet pan method, with the loaf fully exposed to heat, the end result is an ever so slight crusty effect on the loaf because it's directly exposed to heat. A loaf pan, with its high sides will better secure that "loaf shape".