The word is knelt.
The word that means kneel and rhymes with melt is "knelt."
They is actually not any antonym for the word kneel, because they is not word that means exactly the opposite as the word kneel.
Actually, the word "slate" does not rhyme with "kneel," as they have different vowel sounds. "Slate" rhymes with words like "great" and "late."
A word that rhymes with "kneel" and ends with "el" is "reel."
The word that means and rhymes with cloak is "joke."
Means Kneel
The word "afraid" slant rhymes with the word "away" but means scared.
The word that rhymes with angel and means free is "mangel."
The word that rhymes with "creed" and means the opposite of follow is "lead".
One word that rhymes with 'it' and means resist is 'pit'. In this instance the word 'pit' means to set in direct opposition.
kneel to god
The word that means a little wet and rhymes with "boist" is "moist."
The word "lean" fits your criteria as it means cool and rhymes with green.