One website where someone can design a flag is DesignMyOwnFlag.com. Another website is FlagDesigner.Appspot.com. FlagOrder.com has details about the five basic principles when creating a standard flag.
FlagOrder.com states that the design of any flag should be simple in appearance, so much so that a child should have the ability to draw it from memory. The second principle is to translate meanings into colors and patterns. The next step is to use only two to three colors that contrast and stand out in an eye-popping fashion. Basic colors like yellow, red and white are generally used. Text and the use of seals on flags are not recommended. According to FlagOrder.com, writing defeats the purpose of a flag, and seals must be read up close. The last principle is to make the flag unique and not similar to other flags.
HowAny.com notes the three different types of flags: national flags, war flags and international flags. Other flags can derive straight from a person's imagination.
DesignMyOwnFlag.com allows a person to digitally design a flag, starting with defining the height and width of the flag. FlagDesigner.Appspot.com allows the user to imprint various designs and imagery from other flags within such categories as overlay, symbols and flag division.