The first step is choosing what you want to spell out. "Dad," "Daddy," "Grandpa," or "Father," are obvious choices, but you can spell out whatever you like. Words like "Superman" and "My Hero" would also be great choices; the possibilities are endless.
Next, print a photo and put it in the frame you are using. If you are gifting this to your father, a photo of you and your dad or of grandfather/grandchildren would be ideal, etc. You can print the photo at home with your own printer, or get it printed at a photo center.
Finally, lay out the Scrabble pieces on the frame until you are satisfied with the arrangement and glue them in place.
What's the best homemade gift you've ever given? What's the best homemade gift you've ever received?