While I thought that everyone knew how to layer jello...I actually got a lot of questions about this so I am going to show you how I did it! It is really easy but is time consuming since everything has to chill!
I used 6 different jellos for mine. You could probably do the small boxes but my store didn't have all the colors I wanted in that size. I ended up pouring a lot of jello down the sink though.
Make your jello according to the quick set directions on the box. This involves putting ice into it to do a quick chill. Pour the first color into your bowl. I used a trifle bowl but you could use whatever...including individual cups. Put the bowl in the refrigerator and chill for about an hour. Then make the next color and repeat. Repeat. Repeat. Until your bowl is filled or you have all the colors you want!
Before serving you probably want to chill over night.