Traditionally, the flash method involves physical flash cards, which you either make yourself or buy, and which you show rapidly to your child.
Flashing cards (at a speed of less than one second per card) is an effective method of teaching babies, for two reasons:
Information presented at speed is more easily apprehended by the right hemisphere of the brain. Unlike left-brain memorization, which requires conscious, directed effort, right-brain learning is unconscious and effortless.
Children, and especially babies, learn at an extremely rapid pace - much faster than adults; much faster even than adults can imagine. The way to keep a child's attention is to move quickly.
If you want to use physical flash cards, purchasing a set of premade flash cards - with the dots used to represent quantities - will save you considerable time and hassle. You can choose to follow either the Doman method, or the Shichida method, as outlined in the pages that follow.
Alternatively, you can use PowerPoint slideshows, or a specially designed computer-based program such as the Little Math Learning System. By going the virtual route, you won't need to make, buy or store any cards. You'll be able to put together equations instantaneously, and will probably find it easier to give lessons (no more fumbling!). Best of all, systems such as BrillKids' Little Math come with a preinstalled curriculum - all you need to do is sit down with your child, and press play. For more on using the computer to teach math, go to Computer-Based Learning