The next step was to cover the entire area around the letter with a Sharpie dots.
When I had the amount of coverage I wanted I waited for several minutes to allow the marker to dry before peeling off the sticker.
I did the same with each mug and then placed them in the oven at 425 for 30 minutes. Do not preheat the oven, the gradual heating helps the glaze on the mugs to melt and bond with the marker. After thirty minutes turn off the oven, but do not take the mugs out until they are fairly cool. This also helps make the designs permanent.
The finished product turned out great! The blue and the green faded a little, but they look fine, and the red (which many sites claim turns yellow) and purple look amazing!
I also made up little cards to go with them, which you can find here.
Have fun creating your own!