Hash-based signature schemes (HBS) are considered most secure and robust candidates in post-quantum public-key cryptographic schemes. For instance, SPHINCS+ has been chosen in the finalist of NIST post-quantum standardization. Although HBS has a long history in cryptographic research, the early versions of HBS are not practical enough. In this paper, we summarize the main challenges of applying HBS in practice and introduce solutions to improving the early versions to the modern ones.