Pick a design or theme. Flash art is typically meant for mass consumption, so choose a theme that tends to be popular, such as roses, zodiac signs, or tribal designs. Avoid getting too specific. You're not designing one person's tattoo -- you're trying to appeal to a large audience.
Decide on the scope of your flash. A large back or chest piece can take up a whole page. You also could draw several smaller images with one unified theme.
Sketch out the initial design or designs. Draw the design at its smallest possible measurement; the tattoo artist can always enlarge it later. Maintain at least 2 mm of space between lines to keep it a feasible tattoo design.
Ink the outlines of the tattoo design. Keep your lines clear and uniform, since the artist can't "sketch" the design onto skin. Erase any stray pencil marks.
Add color if desired, ensuring that the color is bright and uniform. Avoid fluorescents, metallics and white, as these colors are not typically available in tattoo ink.