Comparison with adverbs

I eat more slowly than my husband does.
A turtle moves more slowly than a rabbit.
My son is more artistic than my daughter.
The Wilsons arrived at the party the earliest of all.
Ann sings the most beautifully of all.
Dick can write the best of all.
Karen pronounces her words more clearly than Mary.
This suitcase is heavier than that one.
This author explains her ideas more clearly than that one.
I like rock music better than classical music.
Bacon is saltier than beef.
Anna pronounces her words the most clearly of all the students in the class

creo que la superlative de "clearly" es "most clearly".  A veces, cuando la superlativia suena raro, en vez de añadir "-est", simplemente decimos "most adverb/adjective". No creo que "clearliest" es una palabra. Por lo menos, no la he escuchado.  Como arriba, escribiste "most slowly' es correcto, no "slowliest" (no correcto).