I don't understand what you're asking.
Seems like you just need to cast on however many stitches you'd like the width to be, then start knitting, and knit until it's as long as you want it.
If you want it extra wide, you can use a large circular needle to hold as many stitches as you like.
A nice pattern I like for washcloths is called "basketweave".
I knit 3, purl 3 for 3 or 4 rows, then switch to purl 3 knit 3....for a few rows (usually 3 or 4, depending on how thick my yarn is). Then back to k3p3 as in row 1. Is this clear? I can post a pic if you like.