To add a level of difficulty. I would add number cube to see how many letters to cover up at a time. Use tally marks, dots, numerals ect Free "find the letter" alphabet worksheets! Get them for uppercase, lowercase, and both!
Cut & Paste Alphabet-Book - This is such a fun way for Preschool and Kindergarten age kids to learn about letters, how to form them, practice making them, and identifying the sounds at the beginning of words!