My suggestion is to find some fonts on your printer that you really like (both upper and lower case) and choose the largest size you can that will fit your mug rug. Then use the printed letters as your pattern and trace onto paper-backed fusible paper. Press each letter onto the BACK of the fabric of your choice. Do a rough cut (leave about 1/8" of fabric all around) to make sure that the fusible really stuck. If not, repress. Then do a final cut. Take off the paper backing and fuse to your mug rug, then topstitch down.