It measured 137x80 studs, or 43.1" x 25.2". I built the perimeter first, mostly with plates, to define the dimensions of the mosaic. I then filled in the space with bricks.

I designed the star using CAD so it has 5 symmetric points (well, close enough considering bricks were used to build it!). The star was built seperately on a baseplate and then was placed in the center of the blue area. Blue bricks were placed around it.

Check out a ton of stuff about the Texas flag, and others, at Farrah Smythe's page.