// This is a part of the controller function from where I am calling below defined methods.
$this->updateBlock();

protected function getBlock() {
    $block = $this->blockManager->createInstance('block_id', []);
    return $block;
}

public function updateBlock() {
    $block = $this->getBlock();
    $this->response->addCommand(new ReplaceCommand('.block--class', $block->build()));
    return $this->response;