namespace CustomModuleBlock;

use MagentoFrameworkViewElementTemplate;
use MagentoCatalogApiProductRepositoryInterface;
use MagentoCatalogModelProduct;


class ImageUploader extends MagentoCatalogBlockProductView
{
    public function __construct(
        MagentoCatalogBlockProductContext $context,
        MagentoFrameworkUrlEncoderInterface $urlEncoder,
        MagentoFrameworkJsonEncoderInterface $jsonEncoder,
        MagentoFrameworkStdlibStringUtils $string,
        MagentoCatalogHelperProduct $productHelper,
        MagentoCatalogModelProductTypesConfigInterface $productTypeConfig,
        MagentoFrameworkLocaleFormatInterface $localeFormat,
        MagentoCustomerModelSession $customerSession,
        ProductRepositoryInterface $productRepository,
        MagentoFrameworkPricingPriceCurrencyInterface $priceCurrency,
        array $data = []
    )
    {
        parent::__construct(
            $context,
            $urlEncoder,
            $jsonEncoder,
            $string,
            $productHelper,
            $productTypeConfig,
            $localeFormat,
            $customerSession,
            $productRepository,
            $priceCurrency,
            $data
        );
    }

    public function process()
    {
        // Return image path here to Jquery Ajax;
    }

    protected function _toHtml()
    {
        $this->setModuleName($this->extractModuleName('MagentoCatalogBlockProductView'));
        return parent::_toHtml();
    }
}

<?php $_product = $block->getProduct(); ?>
<div id="personalise" class="personalise">
    <div class="wrapper">
        <h2>Personalise Your Label</h2>
    <!--- SOme html structure here -->
    </div>
</div>


<script type="text/javascript">
     require(['jquery'], function(jQuery){
         jQuery("button").on('click', function() {
            jQuery.ajax({
              type: "POST",
              url: "<URL_PATH_TO_CUSTOM_PROCESS_BLOCK_ACTION>"
            }).done(function(o) {

              alert("DOne");
            });
            return false;
        });
     });
</script>