I tried to make a belt out of herbs.

The humor in this joke is a prime example of a pun, relying entirely on clever homophonic wordplay. The setup, involving an attempt to create a belt from herbs, perfectly primes the listener for the punchline. The comedic twist comes from the substitution of "waist" (as in, what a belt goes around) for "waste," and "thyme" (a common herb) for "time." This creates a phrase that sounds exactly like the well-known idiom "waste of time," transforming a potentially fruitless endeavor into a linguistic treat.

Puns have been a beloved form of humor for centuries, found in everything from Shakespearean plays to everyday conversation. They thrive on the unexpected double meaning of words, often eliciting groans and chuckles in equal measure. In this case, the context of making a belt out of herbs, while a bit whimsical, provides the ideal real-world connection to the word "waist," making the subsequent "thyme" pun all the more satisfying.

Ultimately, the joke delights in its simplicity and the universal relatability of the idiom it plays upon. It's a quick, lighthearted reminder of how language can be bent and twisted to create a moment of unexpected amusement, proving that sometimes, the best jokes are just a "waist of thyme."