Howdy Collin, and welcome to bonsaiTALK!
The 6:1 ration you hear about is not an absolute rule in bonsai. Rather, it is the suggested ratio for a classic myogi form. A nice bonsai need not have that exact ratio, and the ratio does not guarantee a nice bonsai. (But a thck trunk is a nice thing IMHO).
Cascading styles, literati forms, windswept styles, and many others do not apply the 6:1 ratio.
As to how to get a thick trunk, you can expect almost no thickening once you begin styling. Once in a bonsai pot, expect even less
Growing in the ground is one way to thicken the trunk. I recommend Brent's excellent article on
Developing Large Trunks for Bonsai for more info.
pootsie