To make the process a bit game-like and give the kids a written model to follow, we started by drawing two cards, one for the numerator and the other for the denominator. This would become "their" fraction.
Using grid paper and colored pencils, students used 2 complementary colored pencils to color squares to represent each part of their fraction. I had a color wheel available to teach the concept of opposite colors on the wheel. This lesson was done in small groups so I was able to spend a lot of time using the mathematical vocabulary AND having students use that same vocabulary as they explained to me and each other what they were doing.
When the squares of their "whole" were colored, they cut it out and glued it onto a background. We used 6" X 6" illustration board, but any sturdy paper suitable for watercolor would do.
Next came the watercolor. Students painted shapes that emanated out from their colored pencil areas. This was a good time to talk about brush control and how to lay the brush flat and pull to get straight lines.
This was a two day project for most kids, as we let the paint dry before doing the writing, although some groups did it all in one day.