How to Create Custom CMS Page Layout File in Magento2

If you want to customize your product view for every products then in YOURTHEME/layout/local.xml add :

<catalog_product_view>
    <!-- Allow you to change the global structure of the page -->
    <reference name="root">
        <action method="setTemplate"><template>page/your-custom-layout.phtml</template></action>
    </reference>
    <!-- Allow you to change the content of the product area -->
    <reference name="product.info">
        <action method="setTemplate"><template>catalog/product/your-custom-view.phtml</template></action>
    </reference>
</catalog_product_view>

Feel free to do all the changes you want through local.xml with the catalog_product_view handler.

Then create YOURTHEME/template/page/your-custom-layout.phtml based on template/page/1column.phtml (for example)

And create YOURTHEME/template/catalog/product/your-custom-view.phtml based on template/catalog/product/view.phtml

For magento 2 you have to do it using Helper and controller.

In Controller you have to write in Index.php

<?php 
namespace MageArray\Blog\Controller\Index;
class Index extends \Magento\Framework\App\Action\Action
{
    protected $viewHelper;
    public function __construct(
        \Magento\Framework\App\Action\Context $context,
        \MageArray\Blog\Helper\Index\View $viewHelper,
        \Magento\Framework\View\Result\PageFactory $resultPageFactory
    ) {
        $this->viewHelper = $viewHelper;
        $this->resultPageFactory = $resultPageFactory;
        parent::__construct($context);
    }

    public function execute()
    {
        $page = $this->resultPageFactory->create(false, ['isIsolated' => true]);
        $this->viewHelper->prepareAndRender($page, $this);
        return $page;
    }
}

In namespace MageArray\Blog\Controller\Index;

Here MageArray is my NameSpace, Blog is my Module Name, Index is My controller Ans Class Name "Index" Is My action.

Now Create Helper File as i have View.php Helper and put code as below.

<?php
namespace MageArray\Blog\Helper\Index;
use Magento\Framework\View\Result\Page as ResultPage;
class View extends \Magento\Framework\App\Helper\AbstractHelper
{
    public function __construct(
        \Magento\Framework\App\Config\ScopeConfigInterface $scopeConfig,
        \Magento\Framework\App\Helper\Context $context,
    ) {
        $this->_scopeConfig = $scopeConfig;
        parent::__construct($context);
    }

    public function getStoreConfig($storePath){
        $StoreConfig =  $this->_scopeConfig->getValue($storePath, \Magento\Store\Model\ScopeInterface::SCOPE_STORE);
        return $StoreConfig;
    }

    public function initProductLayout(ResultPage $resultPage,$layout_id)
    {
        $post_list_layout = $this->getStoreConfig($layout_id);
        $pageConfig = $resultPage->getConfig();
        $pageConfig->setPageLayout($post_list_layout);
        $update = $resultPage->getLayout()->getUpdate();
        $controllerClass = $this->_request->getFullActionName();
        return $this;
    }

    public function prepareAndRender(ResultPage $resultPage, $controller)
    {
        $this->initProductLayout($resultPage,'magearray/general/post_list_layout');
        return $this;
    }

}

make changes in namespace, module, helper and configPath names as per your requirements.