When you create your block with $block = $this->_view->getLayout()->createBlock('module\Block\Adminhtml\CustomBlock');$block = $this->_view->getLayout()->createBlock('module\Block\Adminhtml\CustomBlock');
, you can pass data to it using the 3rd argument to the createBlock function. For example:
$block = $this->_view->getLayout()->createBlock('module\Block\Adminhtml\CustomBlock', 'block name', ['data' => ['MyData' => 'value']]);
The data will then be accessible to your block through the $data array that is passed to it's constructor.