Flan molds are de riguer for making Spanish style flan. What is needed is basically a smooth sided dish that can safely be baked. Some people prefer to make several serving-sized flans so that each guest at table gets their own seperate self-contained dessert. Yet a good sized flan can make a beautiful presentation.
Flan dishes may be made of glass, pyrex, porcellain, stainless steel and even have a non-stick teflon coating, though we do not recommend teflon. The key is to have the inside of the dish be smooth so that the flan drops easilly out of the pan in one piece when the dish is turned over onto a plate. Some dishes even come with a lid and a bain marie (which is a kind of water bath that evens out the cooking process) that allows flan to be made on the stove top. As for results, all types will do a good job. The key to good flan is precision in following instructions and meticulousness in attention to the process. What this means is watching the flan closely to remove it from the heat when it is done. You will know that the flan is ready when an inserted knife comes out clean.
English flan, with its flaky crust, generally requires a different style pan. A heavy metal pan with fluted edges does a wonderful job with this style of pastry. The thick metal allows a smooth and even transfer of heat to the flan. A pan that is not damaged by the use of metal utensils is also prefered. With English style flans presentation of the baking dish can be more important so choose one that reflects your taste. Here again, you may wish to avoid teflon, which does prevent sticking, but which generally mars fairly easily. There have been some health risks associated with teflon, though the studies involved are not difinitive.
Flan is fun stuff to make and to eat. Bakeware is a durable product, so take your time in choosing something that you will enjoy using for many years, especially if you are a fan of flan.