Okay, I don't know of any pattern that has that already done for you. So what you need to do is chart your own.
Here's a link that might help -
Basically what you need to do though is figure out how many you're going to cast on, figure how wide the border is going to be, and figure out how large you want the letter within the center. Then you'll have to figure out where the center is on the letter, etc.
Due to the natural nature of stockinette to curl I'll also give you this link. This technique would be cute on a blanket.