@Override
  public long getForkBlock() {
    return JsonUtil.getLong(forkConfigRoot, FORK_BLOCK_KEY)
        .orElseThrow(
            () ->
                new IllegalArgumentException(
                    "Fork block not specified for Clique fork in custom forks"));
  }
Gets fork block.

@return the fork block
config/src/main/java/org/hyperledger/besu/config/CliqueFork.java