How do you manually without a program decrypt a hash value?

Manually decrypting a hash value is generally not feasible due to the one-way nature of cryptographic hashing algorithms, which are designed to be irreversible. However, you can attempt to reverse a hash by using techniques like brute-force attacks, where you generate possible inputs and hash them until you find a match. Alternatively, you can use precomputed tables, like rainbow tables, which contain known hash values and their corresponding plaintexts for common inputs. These methods can be time-consuming and are not guaranteed to succeed, especially with strong hashing algorithms.