Final answer:
The absolute superlative for the Spanish word "feliz" is "felizísimo/a".
Step-by-step explanation:
The absolute superlative for the Spanish word "feliz" (which means "happy") is "felizísimo/a". The spelling change in the absolute superlative involves adding the suffix "-ísimo/a" to the original word. The spelling change includes the removal of the final "z" in "feliz" and replacing it with an "c" before adding the suffix.